Electric wire conductor, covered electric wire, and wiring harness

ABSTRACT

An electric wire conductor having both flexibility and a space-saving property. Also provided are a covered electric wire and a wiring harness containing the electric wire conductor. An electric wire conductor contains a wire strand containing a plurality of elemental wires twisted together. The electric wire conductor has a flat portion in which a cross section intersecting an axial direction of the wire strand has a flat shape. Assuming a conductor cross-sectional area of the flat portion as s mm2 and a vacancy ratio defined as a ratio of vacancies not occupied by the elemental wires in a cross section of the flat portion as v %, the conductor cross-sectional area and the vacancy ratio satisfies v&gt;0.29 s+2.0. The covered electric wire contains electric wire conductor and an insulator covering the conductor. The wiring harness contains the covered electric wire.

This is a Continuation Application of U.S. patent application Ser. No.16/759,987 filed Apr. 28, 2020, which claims the benefit of PCTApplication No. PCT/JP2018/041142 filed Nov. 6, 2018, which in turnclaims the benefit of Japanese Patent Application No. 2017-215294, filedNov. 8, 2017 and Japanese Patent Application No. 2018-094963, filed May16, 2018. The disclosure of the prior applications are herebyincorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to an electric wire conductor, a coveredelectric wire, and a wiring harness, and more specifically, to anelectric wire conductor made of a wire strand, a covered electric wirecontaining an insulator on an outer periphery of the electric wireconductor, and a wiring harness including the covered electric wire.

BACKGROUND ART

A flat cable containing a flat-shaped conductor is commonly known. Aflat cable occupies a smaller space for routing than a conventionalelectric wire configured with a conductor having a substantiallycircular cross section.

As described in Patent Literature 1, a flat rectangular conductor isoften used as a conductor for conventional flat cable. The rectangularflat conductor is made of a single metal wire formed to have arectangular cross section.

CITATION LIST Patent Literature

-   Patent Literature 1: JP 2014-130739 A

SUMMARY OF INVENTION Problems to be Solved by the Invention

A flat rectangular conductor made of a single metal wire hascomparatively high flexibility, and easily bends in a height (thickness)direction of the flat cross section. However, in a width direction ofthe flat cross section, the conductor has low flexibility, and is toorigid to bend easily. Thus, the flat cable having the rectangularconductor made of a single metal wire hardly bends in the particulardirection, which lowers workability of the cable upon routed.

The present invention has been made to solve the above problems, and anobject of the present invention is to provide an electric wire conductorhaving both flexibility and a space-saving property, a covered electricwire, and a wiring harness including such an electric wire conductor.

Means of Solving the Problems

To achieve the objects and in accordance with the purpose of the presentinvention, an electric wire conductor according to the present inventioncontains a wire strand containing a plurality of elemental wires twistedtogether, the conductor having a flat portion where a cross-section ofthe wire strand intersecting an axial direction of the wire strand has aflat shape. Assuming a conductor cross-sectional area of the flatportion as s mm² and a vacancy ratio defined as a ratio of vacancies notoccupied by the elemental wires in a cross section of the flat portionas v %, the conductor cross-sectional area and the vacancy ratiosatisfies v>0.29 s+2.0.

The conductor cross-sectional area and the vacancy ratio preferablysatisfy v≥0.29 s+2.5.

Deformation ratios of the elemental wires from a circle in thecross-section of the flat portion are preferably lower at a part facingan outer periphery of the flat portion than at a center part of the flatportion. Further, the deformation ratios of the elemental wires from acircle in the cross-section of the flat portion at a part facing anouter periphery of the flat portion are preferably 65% or lower ofdeformation ratios of the elemental wires at a center part of the flatportion. Furthermore, the deformation ratios of the elemental wires froma circle in the cross-section of the flat portion at a part facing anouter periphery of the flat portion are preferably 20% or lower.

The electric wire conductor preferably contains a continuous vacancy inthe cross-section of the flat portion which is capable of accommodatingone or more of the elemental wires.

The cross-section of the flat portion preferably includes opposing edgesalong the width direction of the flat shape being parallel to eachother. In this case, the deformation ratios of the elemental wires froma circle in the cross-section of the flat portion are preferably lowerat end parts of the opposing sides of the flat portion than at thecenter part of the flat portion.

A length in the width direction of the flat shape of the flat portion ispreferably three times or more larger than a length in the heightdirection intersecting the width direction.

The cross-section of the flat portion preferably has a quadrangularshape. Further, the cross-section of the flat portion preferably has arectangular shape.

The electric wire conductor preferably contains the flat portion and alow-flatness portion having a flatness lower than the flat portion, theflat portion and the low-flatness portion continuously disposed in theaxial direction.

The number of elemental wires contained in the wire strand is preferably50 or more.

The wire strand is preferably made of copper or a copper alloy and has aconductor cross-sectional area of 100 mm² or larger, or made of aluminumor an aluminum alloy and has a conductor cross-sectional area of 130 mm²or larger.

In the flat portion of the electric wire conductor, the wire strand ispreferably pressed from a first direction and a second directionopposing to each other, and from a third direction and a fourthdirection opposing to each other and intersecting the first directionand the second direction.

A covered electric wire according to the present invention contains theelectric wire conductor as described above and an insulator covering theelectric wire conductor.

A wiring harness according to the present invention contains the coveredelectric wire as described above.

Here, the wiring harness preferably contains a plurality of theabove-mentioned covered electric wires aligned along at least one of awidth direction of the electric wire conductor and a height directionintersecting the width direction. In this case, the wiring harnesspreferably contains at least one of a heat dissipation sheet disposedbetween the plurality of the covered electric wires and a heatdissipation sheet commonly contacting the plurality of the coveredelectric wires.

Further, the plurality of the covered electric wires are preferablyaligned at least along the height direction. In this case, interposingsheets made of a heat dissipation material are preferably disposedbetween the plurality of the covered electric wires aligned along theheight direction. Further, a connection member made of a heatdissipation material is preferably disposed to connect the interposingsheets mutually.

Otherwise, the plurality of the covered electric wires are preferablyaligned at least along the width direction, where the insulator is madeof insulation films and bonded each other by fusion or by adhesive whilesandwiching the electric wire conductors aligned along the widthdirection all together in between the height direction. The electricwire conductors are preferably insulated mutually by the insulation filmor the adhesive.

The wiring harness preferably contains a large cross-section coveredelectric wire and a plurality of small cross-section covered electricwires each having a conductor cross-sectional area smaller than thelarge cross-section covered electric wire, where the small cross-sectioncovered electric wires have a uniform height, and the largecross-section covered electric wire and the small cross-section coveredelectric wires are stacked in the height direction with the smallcross-section covered electric wires are aligned along the widthdirection.

The wiring harness is preferably disposed along an outer periphery of acolumnar member. Alternatively, the wiring harness is preferably housedin a hollow part of a hollow tubular member having an opening along thelongitudinal direction.

Further, the wiring harness is preferably disposed under the floor of anautomobile to constitute a power-supply trunk line. Furthermore, thewiring harness preferably constitutes the ceiling or the floor of anautomobile. In these cases, the wiring harness preferably contains aplurality of the above-mentioned covered electric wires which arealigned at least along the width direction of the electric wireconductor, have uniform length in a height direction intersecting thewidth direction, and are disposed between an interior member and a soundabsorbing member of the automobile so as to dispose the width directionalong surfaces of the interior member and the sound absorbing member.

The wiring harness preferably contains a first covered electric wire anda second covered electric wire, where the first covered electric wire isthe above described covered electric wire having the electric wireconductor made of aluminum or an aluminum alloy, and the second coveredelectric wire has the electric wire conductor made of copper or a copperalloy having a lower flatness and a smaller conductor cross-sectionalarea than the electric wire conductor of the first covered electricwire. In this case, the conductor cross-sectional area of the secondcovered electric wire is preferably 0.13 mm² or smaller.

Advantageous Effects of Invention

The electric wire conductor according to the present invention has highflexibility because it is formed of a wire strand but not of a singlewire. Further, the flat portion having the flat cross sectioncontributes to reduce a space required for routing as an electric wirecompared with a conventional electric wire conductor having asubstantially circular cross section. Furthermore, in a case where theconductor cross-sectional area is made large, a length in the heightdirection can be kept small by increasing a length in the widthdirection of the flat shape, whereby the conductor cross-sectional areacan be increased while maintaining the space-saving property.

In the electric wire conductor according to the present invention, avacancy ratio (v %) of the flat portion defined by the relation with aconductor cross-sectional area (s mm²) of the flat portion is largerthan the lowest value of 0.29 s+2.0, whereby the electric wire conductorhas effectively high flexibility although the cross section of theelectric wire conductor is flat. Accordingly, the electric wireconductor can provide especially great freedom in routing. Further, byobtaining such high vacancy ratio, formation of a sharp protrusion(burr) which might be formed on the peripheral part of the electric wireconductor due to high compression of the electric wire conductor can beprevented.

In the case where the conductor cross-sectional area and the vacancyratio satisfy v≥0.29 s+2.5, the electric wire conductor especially keepshigh flexibility effectively.

When the deformation ratios of the elemental wires from a circle in thecross section of the flat portion are lower at the part facing the outerperiphery of the flat portion than at the center part of the flatportion, intensive deformations of the elemental wires located in theperipheral part and application of a large load to the wires due to thedeformation for forming the wire strand to have a flat cross section canbe prevented. Further, formation of an irregular structure can beprevented including burrs to be formed on the peripheral part of theelectric wire conductor due to the deformation of the elemental wires.

When the deformation ratios of the elemental wires from a circle in thecross section of the flat portion at the part facing the outer peripheryof the flat portion are 65% or lower of the deformation ratios of theelemental wires at the center part of the flat portion, concentration ofthe deformation and the load on the peripheral part of the wire strand,and formation of the irregular structure on the surface of the electricwire conductor are effectively prevented.

When the deformation ratios of the elemental wires from a circle in thecross section of the flat portion at the part facing the outer peripheryof the flat portion are 20% or lower, concentration of the deformationand the load on the peripheral part of the wire strand, and formation ofthe irregular structure on the surface of the electric wire conductorare effectively prevented.

When the electric wire conductor includes a continuous vacancy in thecross section of the flat portion which is capable of accommodating oneor more of the elemental wires, the electric wire conductor can bendflexibly through migration of the elemental wire to the vacancy, thusthe electric wire conductor effectively achieves high flexibility.

When the cross section of the flat portion includes opposing edges beingparallel to each other along the width direction of the flat shape, alarge space can be effectively provided on the outside in the height(i.e., thickness) direction of the electric wire to be routed, whichleads to high space-saving property of the electric wire. In particular,when a plurality of electric wires are stacked when routed, anunnecessary large space is not required.

In this case, when the deformations ratio of the elemental wire from acircle in the cross section of the flat portion at the end parts of theopposing edges being parallel to each other of the flat portion arelower than the deformation ratios of the elemental wires at the centerpart of the flat portion, the concentration of deformation and load onthe end parts of the electric wire conductor can be prevented. Further,an irregular structure including burrs tends to be formed especially onthe end parts of the opposing edges being parallel to each other withinthe peripheral part of the electric wire conductor; however, by keepingthe deformation ratios of the elemental wire at the end parts small, theformation of the irregular structure including burrs on the edge partscan be prevented effectively.

When the length in the width direction of the flat shape of the flatportion is three times or more larger than the length in the heightdirection intersecting the width direction, the electric wire conductorhas high flexibility while having high space-saving property in theheight direction resulting from the smaller length in the heightdirection with respect to the length in the width direction.

Further, when the cross section of the flat portion is a quadrangularshape, useless spaces between electric wires are reduced when aplurality of the electric wires are aligned or stacked, whereby theelectric wires can be assembled densely.

Furthermore, when the cross section of the flat portion is a rectangularshape, useless spaces between the electric wires are especially reducedwhen aligning or stacking a plurality of the electric wires, achievingthe remarkably excellent space-saving property.

When the electric wire conductor contains the flat portion and thelow-flatness portion having a flatness lower than the flat portion thatare disposed continuously in the axial direction, the portions with thedifferent flatness may be disposed in one electric wire conductor,whereby the conductor has the properties of the both portionssimultaneously without a process such as joining. For example, arrangingthe flat portion in a center part of the electric wire conductor, andarranging the low-flatness portions having a substantially circularcross section on both ends of the flat portion can achieve both thespace-saving property at the center part and convenience in attachingmembers such as terminals to the end parts of the electric wireconductor.

When the number of elemental wires contained in the wire strand is 50 ormore, the wire strand can be effectively formed into a flat crosssection without drastically deforming each elemental wire by utilizing achange in the relative arrangement of the elemental wires, while leavinglarge vacancies between the elemental wires. Thus, the electric wireconductor effectively achieves both the space-saving property and theflexibility.

When the wire strand is made of copper or a copper alloy and has aconductor cross-sectional area of 100 mm² or more, or made of aluminumor an aluminum alloy and has a conductor cross-sectional area of 130 mm²or more, the space-saving property and flexibility achieved by the flatcross-sectional shape are particularly effective. For the electric wireconductor having a large cross-sectional area of 100 mm² or more, or 130mm² or more, if the cross section is substantially circular, a largespace is required for routing due to largeness of the diameter and anopposing force against bending becomes large. However, when the crosssection is made flat, the electric wire conductor having such a largecross-sectional area can achieve the space-saving property as well asthe high flexibility especially for the bending in the height direction.

In addition, in the flat portion of the electric wire conductor, whenthe wire strand is pressed from the first direction and the seconddirection opposing to each other, and from the third direction and thefourth direction opposing to each other and intersecting the firstdirection and the second direction, the electric wire conductor can beeffectively formed to have a substantially quadrangle cross section,thus achieving the excellent space-saving property.

Since the covered electric wire according to the present inventioncontains the electric wire conductor as described above, the coveredelectric wire has both flexibility resulting from the electric wireconductor being a wire strand and space-saving property resulting fromthe electric wire conductor having a flat shape. Therefore, in the casewhere the plurality of the covered electric wires are aligned or stackedwhen routed, the routing can be carried out with high degree of freedomwhile saving the space.

The outer surface of the electric wire conductor is a flat surface alongthe width direction of the flat shape, whereby an insulator is easilyformed on each portion of the outer periphery of the electric wireconductor to have a uniform thickness. Accordingly, the insulator may beeasily formed on each portion of the outer periphery of the electricwire conductor to have the smallest thickness required from theviewpoint of wear resistance. Further, the outer surface of theinsulator is also formed to have a flat surface. Accordingly, even ifthe covered electric wire contacts an external object, the contact tendsto occur on the entire flat surface, and a load due to the contact canbe dispersed into a wide area. Thus, the insulator can obtain high wearresistance.

As the wiring harness according to the present invention contains thecovered electric wire containing the flat electric wire conductor asdescribed above, it has excellent flexibility and space-saving property,and thus can be suitably used as a wiring material in a limited spacesuch as an automobile.

Here, when the wiring harness contains a plurality of the coveredelectric wires as described above, and the plurality of the coveredelectric wire are aligned along at least one of the width direction ofthe electric wire conductor and the height direction intersecting thewidth direction, the wiring harness can be formed while reducing thespaces between the plurality of the covered electric wires, thus havingthe remarkably high space-saving property.

In this case, when the wiring harness contains at least one of the heatdissipation sheets interposed between the plurality of the coveredelectric wires and the heat dissipation sheet commonly contacting theplurality of the covered electric wires, even when the plurality of thecovered electric wires are densely arranged to be close to each otherutilizing the space-saving property resulting from the flat shape, theinfluence of heat generated upon application of an electric current canbe suppressed.

Further, when the plurality of the covered electric wires are arrangedat least along the height direction, the covered electric wires can beeffectively routed in a variety of small spaces such as a thin space byutilizing the arrangement of the covered electric wires in the heightdirection.

In this case, when the interposing sheets made of the heat dissipationmaterial are disposed between the plurality of the covered electricwires aligned along the height direction and the connection member madeof the heat dissipation material is disposed to mutually connect theplurality of the interposing sheets, the following effect is obtained:the interposing sheets disposed between the covered electric wireseffectively promote heat dissipation though outward dissipation of theheat generated upon application of a current, which tends to bedifficult in a case where the plurality of the covered electric wiresare arranged closely making their flat wide surfaces to oppose oneanother. Further, the connection member disposed to mutually connect theplurality of the interposing sheets also effectively promotes heatdissipation.

When the plurality of the covered electric wires are aligned at leastalong the width direction, the insulators made of an insulation film areadjoined each other by fusing or adhesion and sandwich the electric wireconductors aligned along the width direction all together from the topand the bottom in the height direction, and the electric wire conductorsare insulated by the insulation film or an adhesive, an insulatorcovering is easily formed on each electric wire conductor with themultiple electric wire conductors each having the flat portion arealigned along the width direction to constitute the wiring harness.Comparing with the case where each electric wire conductor isindividually covered with an insulator, the space-saving property of thewiring harness is enhanced since the thickness of an area occupied bythe insulator covering becomes small and formation of vacancies formedbetween the adjacent insulator coverings is eliminated.

When the wiring harness contains a large cross-section covered electricwire and a plurality of small cross-section covered electric wires asthe covered electric having the flat shape as described above, where thelarge cross-section covered electric wire has a larger cross sectionthan the small cross-section covered electric wire, the smallcross-section covered electric wires are uniform in height, and thelarge cross-section covered electric wire and the small cross-sectioncovered electric wires are stacked in the height direction with thesmall cross-section covered electric wires are aligned along the widthdirection, the small cross-section covered electric wires can be stablydisposed by utilizing the wide outer surface of the large cross-sectioncovered electric wire, constituting the wiring harness excellent inspace-saving property.

When the wiring harness is disposed along the outer periphery of acolumnar member, or the wiring harness is housed in the hollow part of ahollow tubular member having an opening along the longitudinaldirection, the columnar member or the tubular member can be used forsupporting the wiring harness, whereby the routing space of the wiringharness is effectively reduced.

Further, when the wiring harness is disposed under the floor of anautomobile to constitute the power-supply trunk line, compared with aconventional power-supply trunk line using a copper plate, theproductivity can be enhanced and the fatigue fracture due to the enginevibration, for example, can be suppressed.

When the wiring harness constitutes the ceiling or the floor of anautomobile, the space in the automobile can be further effectively usedto provide a wiring route, and the high heat dissipation performance canbe achieved also in the case of applying a large electric current.Further, a ceiling surface or a floor surface of any shape can be formedin accordance with the arrangement of the covered electric wires.

In these cases, the wiring harness may contain the plurality of coveredelectric wires as described above which are aligned at least along thewidth direction of the electric wire conductor, have uniform length inthe height direction intersecting the width direction, and are disposedbetween the interior member and the sound absorbing member of theautomobile so as to dispose the width direction along the surfaces ofthe interior member and the sound absorbing member. In this case, thespace between the interior member and the sound absorbing member can beeffectively used for routing the wiring harness while the distancebetween the interior member and the sound absorbing member is keptsmall. Further, since the height of the plurality of covered electricwires is uniform, the irregular structure of the covered electric wirehardly influences a surface shape of the interior member or a soundabsorbing property of the sound absorbing member.

Further, when the wiring harness contains the first covered electricwire and the second covered electric wire, in which the first coveredelectric wire is the above described covered electric wire having theelectric wire conductor made of aluminum or an aluminum alloy, and thesecond covered electric wire has the electric wire conductor made ofcopper or a copper alloy having a lower flatness and a smaller conductorcross-sectional area than the electric wire conductor of the firstcovered electric wire, the space occupied by the first covered electricwire, which tends to have a large cross-sectional area because of thelow electrical conductivity of aluminum and the aluminum alloy, can bereduced, and simultaneously, characteristics of the second coveredelectric wire brought about by the copper or copper alloy such as thehigh electrical conductivity in the second covered electric wire can beused.

In this case, when the conductor cross-sectional area of the secondcovered electric wire is 0.13 mm² or smaller, the entire wiring harnesscan effectively have a high space-saving property.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of an electric wire conductor according toone embodiment of the present invention.

FIG. 2 is a cross-sectional view of the electric wire conductor.

FIG. 3 is a cross-sectional view which illustrates rolling of a raw wirestrand.

FIGS. 4A to 4D are views showing a variety of cross-sectional shapes ofthe electric wire conductor, and FIGS. 4A to 4D respectively showdifferent shapes. In FIGS. 4B to 4D, elemental wires are omitted.

FIGS. 5A and 5B are cross-sectional views that illustrate examples ofarrangement of covered electric wires in a wiring harness according toone embodiment of the present invention. FIG. 5A illustrates a casewhere the covered electric wires are aligned in a width direction, andFIG. 5B illustrates a case where the covered electric wires are alignedin a height direction.

FIGS. 6A to 6C are cross-sectional views illustrating other examples ofarrangement of the covered electric wires. In FIGS. 6A to 6C, aplurality of small cross-section covered electric wires are stacked on alarge cross-section covered electric wire, and the plurality of smallcross-section covered electric wires have different conductorcross-sectional areas in each Figure.

FIG. 7 is a cross-sectional view showing another embodiment where thecovered electric wires are aligned in the width direction.

FIGS. 8A and 8B are views illustrating examples of routing structure ofthe wiring harness. FIG. 8A illustrates a routing structure with acylindrical member, and FIG. 8B illustrates a routing structure with atubular member having a channel-shaped cross section.

FIGS. 9A to 9F are photographic images of cross sections of the coveredelectric wires with indication of vacancy ratios. FIGS. 9A to 9C eachshow a wire having a conductor cross-sectional area of 60 mm², and thecompression ratios are the following order from the lowest: FIG. 9A, 9B,and 9C. FIGS. 9D to 9F each show a wire having a conductorcross-sectional area of 15 mm², and the compression ratios are thefollowing order from the lowest: FIGS. 9D, 9E, and 9F.

FIG. 10 shows a relation between the conductor cross-sectional area andthe vacancy ratio. The circular marks indicate cases where burrs werenot formed. The rectangular marks indicate cases where burrs wereformed.

FIGS. 11A to 11E are photographic images of cross sections of thecovered electric wires used for evaluation of deformation ratios of theelemental wires, in which regions used for the evaluation are specified.FIG. 11A shows a raw wire strand before pressing (the conductorcross-sectional area: 60 mm²). FIGS. 11B to 11E each show electric wireconductor after pressing. The conductor cross-sectional area is 60 mm²in FIGS. 11B and 11C, 30 mm² in FIG. 11D, and 15 mm² in FIG. 11E. Thecompression ratios are different in FIGS. 11B and 11C.

FIG. 12 shows simulation results regarding a temperature rise of thecovered electric wires.

FIGS. 13A to 13C are photographic images of cross sections of samplesused for evaluation of wear resistance. FIGS. 13A to 13C show samples 1to 3, respectively.

DESCRIPTION OF EMBODIMENTS

Hereinafter, detailed descriptions of an electric wire conductor, acovered electric wire, and a wiring harness according to one embodimentof the present invention will be provided with reference to FIGS. 1 to13. A covered electric wire according to one embodiment of the presentinvention contains an electric wire conductor according to oneembodiment of the present invention and an insulator covering theconductor. In addition, a wiring harness according to one embodiment ofthe present invention contains a plurality of covered electric wiresassembled together containing the covered electric wire according to oneembodiment of the present invention.

[Electric Wire Conductor]

FIG. 1 is a perspective view of an external appearance of an electricwire conductor 10 according to one embodiment of the present invention.FIG. 2 shows a cross section perpendicularly intersecting an axialdirection (longitudinal direction) of the electric wire conductor 10.

(1) Cross-Sectional Shape of the Electric Wire Conductor

The electric wire conductor 10 is configured as a wire strand containinga plurality of elemental wires 1 twisted together. Further, at least apart of the electric wire conductor 10 along the axial direction has aflat outer shape. In other words, the electric wire conductor 10 has aflat portion where a cross section perpendicularly intersecting theaxial direction of the electric wire conductor 10 is flat. In thepresent embodiment, the entire electric wire conductor 10 along theaxial direction is formed as the flat portion.

Here, the concept that “the cross section of the electric wire conductor10 is flat” describes a state where a width W, which is a length of thelongest line among lines that pass through the cross section in parallelto edges constituting the cross section and encompass the entire crosssection, is larger than a height H, which is a length of a lineperpendicular to the above-mentioned longest line and encompass theentire cross section. In the cross section of the electric wireconductor 10 according to the present embodiment shown in FIG. 2, and ineach of the cross sections of the electric wire conductors in theembodiments shown in FIGS. 4A to 4D, the width W is larger than theheight H.

While the cross section of the electric wire conductor 10 may have anyspecific shape as long as it is flat, the cross section of the electricwire conductor 10 in the present embodiment has opposing edges 11 and 12that are parallel to each other along a direction of width W (widthdirection x) of the flat shape. In other words, two parallel lines 11and 12 can be drawn in the width direction x, so as to circumscribe theouter elemental wires 1 forming the cross section of the electric wireconductor 10. In the present description, concerning the shape of theelectric wire conductor 10, concepts for describing relationships amonglines and surfaces such as parallel and vertical may include a deviationwith reference to the concepts in geometry such as a deviation at anangle of approximately plus or minus 15 degrees, or an R shape whereeach corner is rounded. In addition, concepts of edges, straight lines,plain surfaces, or the like may include a curved line or a curvedsurface with a deviation at an angle of approximately plus or minus 15degrees from a geometric straight line or a plain surface.

In the present embodiment, the cross section of the electric wireconductor 10 has a rectangular shape. In the Figures, the number ofelemental wires 1 contained in the electric wire conductor 10 is reducedfor easier understanding.

As the electric wire conductor 10 according to the present embodimenthas a flat cross section, when it is routed in a form of the coveredelectric wire, for example, a space necessary for routing may be madesmaller than a case of routing an electric wire having a substantiallycircular cross section of the same conductor cross-sectional area as theelectric wire conductor. In other words, spaces around an electric wirein which other electric wires or other members are not allowed to bedisposed can be reduced. In particular, a space occupied by the electricwire in a height direction y can be made smaller. Thus, the electricwire effectively achieves a space-saving property. Consequently, otherelectric wires or other members can be sufficiently disposed in a spacevertically provided in the height direction (±y direction) outside ofthe electric wire. For example, in the case of routing the electric wirealong a surface for routing, when a flat surface of the electric wire,that is, a surface parallel to the width direction x is arranged alongthe surface for routing, it is possible to effectively provide a spaceabove the electric wire (in a direction opposing to the surface forrouting, having the electric wire therebetween). Further, in a casewhere a conductor cross-sectional area of the electric wire conductor 10is desired to be large, the space-saving property in the heightdirection y can be maintained by making the width W large while keepingthe height H small.

In particular, the electric wire conductor 10 having opposing edges 11and 12 parallel to the width direction x in its cross section canprovide a large space vertically in the height direction (±y direction)outside the routed electric wire, whereby an excellent space-savingproperty is achieved. Especially, in the case of assembling a pluralityof electric wires by stacking one electric wire on another electricwire, spaces between the plurality of electric wires along the heightdirection y can be reduced. Here, the concept of “assembling a pluralityof electric wires” includes both of a configuration where a plurality ofelectric wires are integrally bundled with an insulation material, forexample, and a configuration where a plurality of independent electricwires are closely disposed.

Furthermore, the electric wire conductor 10 having a rectangular crosssection can provide a large space vertically (±y direction) andlaterally (±x direction), whereby the space-saving property is furtherimproved. Especially, in the case of assembling the plurality ofelectric wires with stacking one electric wire on another electric wire,or with aligning one electric wire laterally to another electric wire,spaces between the plurality of electric wires along the heightdirection y and the width direction x can be reduced.

As described above, the electric wire conductor 10 according to thepresent embodiment contains the wire strand containing a plurality ofelemental wires 1 twisted together, and the wire strand has a flat outershape. Therefore, the electric wire conductor 10 has excellentflexibility in each direction. Patent Literature 1 discloses arectangular conductor that has flexibility in the height direction to acertain degree, but shows low flexibility in the width direction and istoo rigid to bend easily in the width direction. In contrast, theelectric wire conductor 10 according to the present embodiment includingthe wire strand has the excellent flexibility and easily bends in thewidth direction x as well as the height direction y.

Thus, the electric wire conductor 10 according to the present embodimentcan achieve both the flexibility, which provides freedom in routing, andthe space-saving property. In an automobile, for example, due to recenthigh functionalization, the number of electric wires and components tobe disposed is increasing. Also, a larger electric current is demandedfor vehicles such as electric vehicles, which results in enlargement ofa diameter of the electric wire, whereby a space for routing individualelectric wires has been reduced. However, the electric wire conductor 10according to the present embodiment can effectively use a small spacewhen routed because of the space-saving property and the excellentflexibility. In the case of assembling a great number of electric wires,or using an electric wire having a large conductor cross-sectional area,this advantage is especially enhanced.

In the above-described embodiment, the electric wire conductor 10 has arectangular cross section. However, as described above, the crosssection of the electric wire conductor 10 may be of any shape as long asit is flat. FIGS. 4B to 4D show other examples of the cross-sectionalshape. Here, in FIGS. 4B to 4D, the elemental wires 1 are omitted toshow only the outer shape of the cross section, that is, a circumscribededges which approximate cross sections of the electric wire conductors.FIG. 4B shows a cross section in an ellipse shape (a shape of arectangle with half circles attached to both ends). As a cross sectionin a quadrangle shape other than the above-mentioned rectangular shape,FIG. 4C shows across section in a trapezoidal shape, and FIG. 4D shows across section in a parallelogram shape. Since the electric wireconductor 10 has a quadrangle cross section, a great number of electricwire conductors 10 may be disposed in the height direction y and thewidth direction x with small spaces, which contributes to the excellentspace-saving property for assembling a great number of electric wires.This advantage is especially remarkable when the cross-sectional shapeis a rectangle as described above.

(2) Vacancy in the Cross Section of the Electric Wire Conductor

Further, the electric wire conductor 10 according to the presentembodiment has a vacancy ratio at the cross section of the flat portionwhich is higher than a predetermined lowest value defined according tothe conductor cross-sectional area. The vacancy ratio at the crosssection of the electric wire conductor 10 is defined as, within thecross section of the electric wire conductor 10 perpendicularlyintersecting the axial direction, a proportion of an area of vacancy notoccupied by the elemental wires 1 to an entire area of the wholeelectric wire conductor 10, that is, an area of a region surrounded bythe outline of the entire electric wire conductor 10. The conductorcross-sectional area is an area of a region occupied by the elementalwires within the cross section of the electric wire conductor 10.

The vacancy ratio required for allowing the electric wire conductor 10to have sufficient flexibility varies depending on the conductorcross-sectional area. As the conductor cross-sectional area becomeslarge, the electric wire conductor 10 becomes hard to bend, with theresult that the conductor 10 needs to have high vacancy ratio to obtainhigh flexibility. As will be described in Examples below, a linearrelation exists between a conductor cross-sectional area and a requiredvacancy ratio. When the relation represented by the following formula(1), where the vacancy ratio of the cross section of the electric wireconductor 10 is v % and the conductor cross-sectional area is s mm², issatisfied, the electric wire conductor 10 can obtain sufficientflexibility:

V>0.29 s+2.0   (1)

As described above, the electric wire conductor 10 has high flexibilityboth in the height direction y and the width direction x because of itsflat shape, and it can easily bend. By having sufficient vacancy definedby the above formula (1) in the cross section of the electric wireconductor 10, the elemental wires 1 can move in the electric wireconductor 10 using the vacancy when the electric wire conductor 10 bendsalong the height direction y or the width direction x, so that theelectric wire conductor 10 can bend more easily. Thus, the flexibilityof the electric wire conductor 10 is improved.

By satisfying the relation indicated by the above formula (1), theelectric wire conductor 10 according the present embodiment obtains highflexibility and suppresses an unnecessary irregular structure such asburrs from formed on the peripheral part of the conductor. As will bedescribed later, when the electric wire conductor 10 is formed, forexample, by pressing a raw wire strand 10′, as the compression ratiobecomes high, the vacancy ratio of the cross section of the electricwire conductor 10 becomes low and the irregular structure such as burrseasily formed on the peripheral part of the conductor. In other words,the electric wire conductor 10 with little irregular structure such asbars has a high vacancy ratio and achieves high flexibility.

From the viewpoint of further increasing flexibility of the electricwire conductor 10, the vacancy ratio preferably satisfies a relationrepresented by the following formula (2):

V≥0.29 s+A   (2)

where A is a constant number, and A=2.5. The electric wire conductor 10achieves especially high flexibility when A=3.5 in the above formula(2).

When preferable vacancy ratios (v %) are represented by numeric valuesaccording to the conductor cross-sectional area (s mm²), the values willbe as follows:

S≤15 mm²: v≥6%, preferably v≥8%

15 mm²<s≤30 mm²: v≥11%, preferably v≥12%

30 mm²<s≤50 mm²: v≥16%, preferably v≥18%

50 mm²<s≤60 mm²: v≥19%, preferably v≥21%

The highest value of the vacancy ratio is not particularly limited.However, from the viewpoint of easiness in forming the wire strand 10having a flat shape such as by pressing, and maintaining the flat shape,it is preferable that the vacancy ratio satisfies the following formula(3):

v≤0.29 s+B   (3)

where B is a constant number, and B=11.

In the cross section of the electric wire conductor 10, small vacanciesare provided in a region between each of the elemental wires 1. Thevacancy ratio as defined above is a ratio of the area of these smallvacancies in total with respect to the cross-sectional area of theelectric wire conductor 10. When the total area of these small vacanciesis equal to or more than the predetermined proportion in the crosssection of the electric wire conductor 10, the flexibility of theelectric wire conductor 10 is improved. In addition, sizes of therespective vacancies in the region between each of the elemental wires 1also contributes improvement in flexibility of the electric wireconductor 10. In other words, a state where vacancies of a certain sizeare provided in the cross section of the electric wire conductor 10 as acontinuous region can improve the flexibility of the electric wireconductor 10 more effectively than a state where minute vacancies areevenly spread over the cross section of the electric wire conductor 10.Specifically, the cross section of the electric wire conductor 10preferably contains a continuous vacancy such that one or more, two ormore, or three or more of the elemental wires 1 can be accommodatedtherein. This is because the elemental wires 1 moving into such a largevacancy enables flexible bending of the electric wire. Here, anelemental wire 1 used for judging whether the certain vacancy is capableof accommodating the elemental wire may be an elemental wire 1surrounding the vacancy, or an elemental wire having a circular crosssection with the same cross-sectional area as that of any elemental wire1 forming the electric wire conductor 10. For example, in FIG. 4A, avacancy indicated by a reference sign v is capable of accommodating twoor more of the elemental wires. Even where continuous vacancies withsize and shape which is capable of accommodating the elemental wires 1are not formed in the cross section of the elemental wire conductor 10,it is still preferable that continuous vacancies having the size of anarea in which one or more, two or more, or three or more of theelemental wires, when converted into the cross-sectional area of theelemental wire 1, are formed in the cross section of the electric wireconductor 10.

For calculation of the area of the electric wire conductor 10 and thearea of the vacancies, the electric wire conductor 10 or the coveredelectric wire 20 having the insulator 21 on the outer periphery of theelectric wire conductor 10 may be subjected to processes such as cuttingand polishing to obtain a cross section, and then, such a cross sectionis photographed for actual measurement. In the preparation of the crosssection, the electric wire conductor 10 and the covered electric wire 20may be embedded in transparent resin for example prior to the operationincluding cutting as appropriate, to prevent a change in the shape orthe area of the vacancies due to the operation including cutting. Forpreparing a sample that enables accurate evaluation of the state of thecross section of the vacancies, the electric wire conductor 10 or thecovered electric wire 20 is preferably put, at the time of embedded inresin, in a container with the flat surface of the electric wireconductor 10 facing the container. Further, upon embedding, thecross-section polishing of the sample is preferably performed to aposition away from the cut surface to form a sample for evaluation.Further, the area of the electric wire conductor 10 and the area of thevacancy may be evaluated for the entire cross-section of the electricwire conductor 10, or alternatively, in order to eliminate influence ofthe irregular structure in an outermost periphery of the electric wireconductor 10, the areas of the electric wire conductor 10 and thevacancies may be evaluated for an inner region where the outermostperiphery of the electric wire conductor 10 is excluded, instead ofevaluating the whole cross section if the elemental wires 1 aresufficient in number such as equals to or more than 50.

(3) Cross-Sectional Shape of Each Elemental Wire

For the electric wire conductor 10 according to the present embodiment,the cross-sectional shape of each elemental wire 1 constituting theelectric wire conductor 10 may be of any shape as long as the outershape of the entire electric wire conductor 10 is flat. A conventionalelectric wire having a substantially circular cross section may beemployed as the elemental wire 1 in the present embodiment. However, atleast a part of the plurality of elemental wires 1 may have crosssections of shapes deviated from a circle, such as flat shapes. As willbe described later, when a raw wire strand 10′ is pressed into a flatshape, at least a part of the elemental wires 1 may be deformed intoflat shapes, depending on, for example, the material constituting theelemental wires 1.

For the electric wire conductor 10 according to the present embodiment,in the cross-section perpendicularly intersecting the axial direction,deformation ratios of the elemental wires 1 are lower at a peripheralpart facing the outer periphery of the electric wire conductor 10 thanat a center part which is located inside of the peripheral part. FIGS. 1and 2 schematically show distribution of the deformation ratio of suchelemental wires 1.

Here, the deformation ratio of an elemental wire 1 is an index showing adegree of deviation from a circle for a cross section of a certainelemental wire 1. For an elemental wire 1 actually contained in theelectric wire conductor 10, a longest diameter L is defined as a lengthof the longest line laterally crossing the cross section, and a diameterR is defined as a diameter of a circle having the same area as thecross-sectional area of the elemental wire 1. Then, a deformation ratioD of the elemental wire 1 is represented as follows:

D=(L−R)/R×100%   Formula (4)

The diameter R may be obtained by measuring a cross-sectional area ofthe elemental wire 1, or alternatively, if a diameter of the elementalwire 1 before deformed such as as by pressing is known, or if a portionin which the elemental wires 1 are not deformed (corresponding to alow-flatness portion as will be described later) is also included in thesame electric wire conductor 10, a diameter of the elemental wire 1which is not deformed may be used as the diameter R. Further, onlyelemental wires 1 disposed on the outermost periphery of the electricwire conductor 10 may be employed as the elemental wires 1 in theperipheral part, and only elemental wires 1 disposed in the center ofthe electric wire conductor 10 may be employed as the elemental wires 1in the center part. However, from the viewpoint of reducing influence ofvariation in deformation of the elemental wires 1, the deformation ratioD is preferably obtained as an average value of a plurality of elementalwires 1 included in a region having a certain area. For example, regionssurrounded by a rectangle with edges in a length of approximately 10 to30% of the width W of the electric wire conductor 10, or regionssurrounded by a circle having a diameter of approximately 10 to 30% ofthe width W may be employed including the outermost periphery or thecenter of the electric wire conductor 10, and such regions may bedefined as the peripheral part and the center part, respectively.

The cross section of the electric wire conductor 10 according to thepresent embodiment having a flat shape can be formed more efficiently ifthe elemental wires 1 located in the upper and lower direction (±ydirection) of the peripheral part of the electric wire conductor 10 aredeformed into flat shapes than in the case where the elemental wires 1located in the center part are deformed. However, if the elemental wires1 in the peripheral part are intensively deformed, loads areconcentrated on these elemental wires 1, whereby physical properties ofthe elemental wires 1 in the peripheral part of the electric wireconductor 10 become significantly different from those of the innerregion. Further, since the shape of the elemental wires 1 in theperipheral part, especially in the outermost periphery defines the outershape of the entire electric wire conductor 10, drastic deformation ofsuch elemental wires 1 possibly causes an unnecessary irregularstructure to be formed on the outer surface of the electric wireconductor 10. Such an irregular structure includes burr that maypossibly be formed during processing of the raw wire strand 10′ into aflat shape. The burr tends to be formed especially on end parts of theelectric wire conductor 10 in the width direction (±x direction). It ispreferable that burrs are not formed on the peripheral part of theelectric wire conductor 10. Few irregular structures such as burrs onthe electric wire conductor 10 as described above may be an indexshowing excellent flexibility of the electric wire conductor 10.

Meanwhile, in the electric wire conductor 10, making the deformationratio of the elemental wire 1 at the peripheral part smaller than thedeformation ratio of the elemental wire 1 at the center part can preventconcentration of the loads for deformation to the elemental wires 1 inthe peripheral part and the formation of the unnecessary irregularstructure on the outer periphery of the electric wire conductor 10. Asdescribed above, since the vacancy ratio defined by the formula (1) isensured in the electric wire conductor 10 according to the presentembodiment, and the elemental wires 1 may be arranged in variousrelative locations because of presence of the vacancies between theelemental wires 1, the cross section of the electric wire conductor 10can be formed into a desired flat shape depending on the relativearrangement of the elemental wires 1, without drastic deformation of theshapes of each elemental wires 1.

From the viewpoint of effectively preventing the concentration of theloads for deformation to the elemental wires 1 at the peripheral part ofthe electric wire conductor 10 and the formation of the unnecessaryirregular structure on the surface of the electric wire conductor 10, aratio of the deformation ratio of elemental wire 1 at the peripheralpart to the deformation ratio of elemental wire 1 at the center part(i.e., peripheral deformation ratio; deformation ratio at the peripheralpart/deformation ratio at the center part×100%) is preferably 70% orlower, more preferably 65% or lower, still more preferably 50% or lower,and still further more preferably 25% or lower. In addition, a value ofthe deformation ratio of the elemental wire 1 at the peripheral part ispreferably 20% or lower, more preferably 10% or lower, and still morepreferably 5% or lower. It is preferable that the deformation ratio ofthe elemental wire 1 at the peripheral part is as small as possible, andthe lower limit of the deformation ratio is not particularly specified.

The deformation ratio of the elemental wire 1 in the center part is notspecifically limited; however, from the viewpoint of preventingapplication of loads to the elemental wire 1 due to excessivedeformation, the deformation ratio of the elemental wire 1 in the centerpart is preferably 50% or lower, and more preferably 30% or lower. Onthe other hand, from the viewpoint of effectively forming the crosssection of the electric wire conductor 10 to have the flat shape whilesuppressing the deformation of the elemental wire 1 in the peripheralpart, the deformation ratio at the center part is preferably 10% orhigher, and more preferably 20% or higher.

When the cross section of the electric wire conductor 10 containsopposing edges 11 and 12 parallel to the width direction x, especially,when the cross section of the electric wire conductor 10 has arectangular shape, it is preferable that the deformation ratios of theelemental wires 1 at end parts in the width direction of the crosssection, that is, at both end parts of the parallel opposing edges 11and 12 are kept particularly low. This is because, when the crosssection of the electric wire conductor 10 is formed into such a shape,in order to form the parallel opposing edges 11 and 12 along the widthdirection x, and to form a corner structure of an approximately rightangle, the deformation ratio at the end parts in the width directiontends to be high. Further, processes for formation of the electric wireconductor 10 such as compression of the raw wire strand 10′ possiblycauses sharp burrs in the end parts. From the viewpoint of preventingthose phenomena, in the cross section of the electric wire conductor 10,the deformation ratios of the elemental wires 1 particularly at the endparts in the peripheral part are preferably 70% or lower, morepreferably 50% or lower, and still more preferably 25% or lower of thedeformation ratios of the elemental wires 1 at the center part. Inaddition, a value of the deformation ratios of the elemental wires 1 atthe end parts is preferably 20% or lower, more preferably 10% or lower,and still more preferably 5% or lower. Further, when the deformationratios of the elemental wires 1 are compared within the peripheral partbetween the end parts and the side parts, it is preferable that thedeformation ratio at the end parts is lower than the deformation ratioat the side parts, where the side parts mean intermediate parts of theopposing edges 11 and 12 along the width x direction excepting the endparts. In other words, the deformation ratios are preferably in thefollowing order, from the lowest: the end part, the side part, and thecenter part.

In the electric wire conductor 10, as the number of the elemental wire 1is increased, it becomes easier to form the cross section into a flatshape while keeping the deformation ratios of the elemental wires 1 atthe peripheral part lower than those at the center part and maintainingthe high vacancy ratio such as the one defined by the formula (1). Forexample, when the number of the element wire 1 is 50 or more, thecondition as above can be sufficiently achieved owing to variation inrelative arrangements of the elemental wires 1. On the other hand, whenthe number of the elemental wire 1 is less than 50, it is stillpreferable to ensure the vacancy ratio defined by the formula (1) forthe purpose of obtaining the sufficient flexibility of the electric wireconductor 10, even if the elemental wires 1 in the peripheral part aredeformed at a deformation ratio equivalent to or higher than theelemental wires 1 in the center part.

(4) Material and Conductor Cross-Sectional Area of the Electric WireConductor

The elemental wires 1 constituting the electric wire conductor 10 may bemade of any conductive material such as a metal material. Examples oftypical material constituting the elemental wire 1 may contain copper, acopper alloy, aluminum, and an aluminum alloy. These metal materials aresuitable for the electric wire conductor 10 according to the presentembodiment in that processes of forming the wire strand and pressinginto a flat shape are easy to be carried out, and the flat shape is easyto be maintained. As the elemental wires 1 constituting the electricwire conductor 10, the elemental wires all made of the same material maybe used, or a multiple kinds of elemental wires made of differentmaterials may be mixed.

The conductor cross-sectional area of the electric wire conductor 10 maybe appropriately selected according to a desired electricalconductivity, for example. As described above, in the electric wireconductor 10, as the number of the elemental wire 1 is increased, itbecomes easier to form the cross section into a flat shape while keepingthe deformation ratios of the elemental wires 1 at the peripheral partlower than those at the center part and maintaining the high vacancyratio such as the one defined by the formula (1). As the conductorcross-sectional area large, it becomes easier to increase the number ofthe elemental wires 1 contained in the electric wire conductor 10, andthus the cross section of the electric wire conductor 10 is easilyformed into a flat shape while suppressing deformation of the elementalwires 1 in the peripheral part and maintaining vacancy ratio. From sucha viewpoint, a preferable cross-sectional area of the conductor is 5 mm²or larger and more preferably 10 mm² or larger.

The larger the conductor cross-sectional area is, the easier it becomesto form the flat shape by processes such as pressing, and the flat shapeonce formed can be firmly maintained.

From such a viewpoint, more preferable conductor cross-sectional areais, for example, 16 mm² or more when the elemental wires 1 constitutingthe electric wire conductor 10 are made of copper or a copper alloy, and40 mm² or more when the elemental wires 1 are made of aluminum or analuminum alloy.

Further, in a case where the conductor cross-sectional area is as largeas 100 mm² or more, if the electric wire conductor has a substantiallycircular cross section, a diameter of the circular cross section becomeslarge so that a large space is required for routing, and an opposingforce incurred upon bending becomes large, whereby it becomes difficultto ensure the flexibility sufficient for routing. In contrast, theelectric wire conductor 10 having the flat cross section enables theheight H to be kept smaller than in the case of the electric wireconductor having the substantially circular cross section with the sameconductor cross-sectional area. Thus, a space in the height direction yoccupied by the electric wire conductor 10 is reduced, the opposingforce generated upon bending along the height direction y becomessmaller, whereby the flexibility required for routing is efficientlyachieved. Also, by forming the cross-sectional shape of the electricwire conductor 10 with a large conductor cross-sectional area into flat,a heat dissipation performance of the electric wire conductor 10 isenhanced. From the viewpoint of effectively utilizing these advantagessuch as ensuring the flexibility, the conductor cross-sectional area ispreferably 100 mm² or larger when the electric wire conductor 10 is madeof copper or a copper alloy. The conductor cross-sectional area ispreferably 130 mm² or larger when the electric wire conductor 10 is madeof aluminum or an aluminum alloy. The electric wire conductor 10 havingsuch a large conductor cross-sectional area is anticipated forapplication to a power supply wire for an electric vehicle of highoutput, for example. Since the power supply wires are required to berouted in a limited space in the vehicle, the space-saving property andflexibility of the electric wire conductor 10 having a flat crosssection are advantageous. In particular, from the viewpoint of reducingvehicle weight, it is effective to form the electric wire conductor 10having a large conductor cross-sectional area from aluminum or analuminum alloy; however, since aluminum and an aluminum alloy have alower electrical conductivity than copper and a copper alloy, theelectric wire conductor 10 having a particularly large conductorcross-sectional area such as 130 mm² or more is needed for obtaining therequired electrical conductivity.

Furthermore, preferable outer diameter of each elemental wire 1contained in the electric wire conductor 10 is 0.3 to 1.0 mm, forexample. The number of elemental wires 1 contained in the electric wireconductor 10 is determined depending on the conductor cross-sectionalarea of the electric wire conductor 10 and the outer diameter of theelemental wires 1 to be used. Meanwhile, as the number of elementalwires 1 is increased, the elemental wires 1 maybe disposed in morevarious relative positions, which makes it easier to form the electricwire conductor 10 to have the flat cross section while ensuring the highvacancy ratio as the one defined by the formula (1), and further keepingthe deformation ratio of the elemental wires 1 at the peripheral part ofthe electric wire conductor 10 low. From this viewpoint, the number ofelemental wires 1 is preferably 50 or more, more preferably 100 or more,and still more preferably 500 or more.

(5) Aspect Ratio of the Electric Wire Conductor

For the cross section of the electric wire conductor 10, an aspect ratio(H:W) of the flat shape may be appropriately selected in considerationof a desired space-saving property, for example. The range of 1:2 to 1:8may be provided as an example of the aspect ratio. Within this range,the wire strand can be effectively formed into the flat shape whileobtaining the high space-saving property. Further, in a case where theelectric wire conductor 10 is used for wiring in an automobile, forexample, a configuration in which a height H is 3 mm or smaller may beprovided as a preferable example.

As will be described later, when a raw wire strand 10′ formed of aconventional wire strand having a substantially circular cross sectionis subjected to pressing to form the electric wire conductor 10 having aflat cross section, vacancies between the elemental wires 1 tend to besmaller as the rolling process proceeds. Especially, the higher theaspect ratio of the flat cross section of the electric wire conductor 10is (the width W is larger in comparison with the height H), the lowerthe vacancy ratio tends to be. However, when the vacancy ratio definedby the formula (1) as described above is ensured in the case where theaspect ratio (H:W) is 1:3 or higher, that is, the width W of theelectric wire conductor 10 is three times or more larger than the heightH, for example, the electric wire conductor 10 can effectively achieveboth the high space-saving property and the flexibility.

Further, by forming the electric wire conductor 10 to have a flat crosssection, a surface area becomes large compared with the substantiallycircular cross section, which enhances the heat dissipation performanceof the electric wire conductor 10. As a result, when a same amount ofelectrical current is applied, a temperature rise of the electric wireconductor 10 having a flat cross section is smaller than in the casewhere the conductor has a circular cross section. In other words, whenan upper limit of temperature rise is determined, a same amount ofelectrical current can be applied to the electric wire conductor 10having a flat cross section with a conductor cross-sectional areasmaller than that having a substantially circular cross section, whilesuppressing the temperature rise within a range below the upper limit.As the aspect ratio of the electric wire conductor 10 is increased, aneffect of improving the heat dissipation performance is enhanced. Forexample, as will be described in Examples below, when the aspect ratiois 1:3 or higher, even if the conductor cross-sectional area of theelectric wire conductor 10 having a flat cross section is 90% of that ofthe electric wire conductor 10 having an approximately circular crosssection, the temperature rise can be suppressed to the same degree.Further, the aspect ratio is preferably 1:5 or higher.

(6) Other Embodiments

Hereinbefore, the embodiment has been described in which the entireregion of the electric wire conductor 10 in the axial direction consistsof the flat portion having a flat cross section. However, the flatportion may constitute apart of the entire region in the axial directionof the electric wire conductor 10. That is to say, the flat portion anda low-flatness portion having a flatness (i.e., a ratio of W to H) lowerthan the flat portion may be arranged adjacent to each other along theaxial direction of the electric wire conductor 10, for example. The flatportion and the low-flatness portion consist of common elemental wires 1integrally continuous therethrough, and have different cross-sectionalshapes. The low-flatness portion has a cross section approximatelycircular having a flatness of substantially one. By disposing the flatportion and the low-flatness portion continuously in one electric wireconductor 10, the electric wire conductor 10 can obtain both propertiesprovided by the flat portion and the low-flatness portion withoutprocess such as joining.

At the low-flatness portion, since the flatness of the electric wireconductor 10 obtained through process such as pressing is small, it ispreferable that the deformation ratio of the elemental wire 1 is smallerthan that in the flat portion, accordingly. In particular, in thelow-flatness portion having a substantially circular cross section withthe flatness of substantially one, it is preferable that the elementalwires 1 also have substantially circular cross sections.

The flat portion and the low-flatness portion may be disposed along theaxial direction of the electric wire conductor 10 in any order. However,a configuration in which the flat portion is disposed in the center partof the axial direction and the low-flatness portions having asubstantially circular cross section are disposed on both ends thereofcan be presented as a preferred example. In this case, the flat portioncan be used for routing in a limited space, and simultaneously othermembers such as terminals are attached to both ends of the low-flatnessportions. Thus, it is possible to utilize both the space-saving propertyand the flexibility of the flat portion, as well as convenience ofattaching the other members to the low-flatness portions having acircular or substantially circular cross section. Further, in the flatportion, a plurality of portions with different flatness may be disposedadjacent to each other.

[Production Method of Electric Wire Conductor]

As shown in FIG. 3, the electric wire conductor 10 according to thepresent embodiment can be formed by pressing a raw wire strand 10′ whichcontains a plurality of elemental wires 1 twisted together and has asubstantially circular cross section. For pressing, forces F1 and F2 areapplied from a first direction and a second direction opposing oneanother that are perpendicular to the axial direction of the raw wirestrand 10′ to compress the raw wire strand 10′, so as to obtain a flatelectric wire conductor 10 in which an applying direction of the forcesF1 and F2 corresponds to the height direction y.

Further, in addition to the forces F1 and F2 applied from the firstdirection and the second direction, forces F3 and F4 are applied to theraw wire strand 10′ from a third direction and a forth directionopposing one another and intersecting the first and second directions,so as to effectively form electric wire conductor 10 to have aquadrangular cross section. Especially, by applying the forces F3 and F4from directions perpendicular to the forces F1 and F2, the electric wireconductor 10 is effectively formed to have a rectangular cross section.In this case, by making the forces F1 and F2 larger than the forces F3and F4, the electric wire conductor 10 with a high flatness (i.e., theratio of W to H is large) can be obtained. Further, the forces F1 andF2, and the forces F3 and F4 may be applied simultaneously; however, byapplying the forces F1 and F2 first, and then applying the forces F1′and F2′ from the same directions as the forces F1 and F2 simultaneouslywith the forces F3 and F4, the electric wire conductor 10 with the highflatness can be obtained, in which the cross section is firmly formedinto a quadrangular shape (especially, a rectangular shape). In the caseof changing the flatness along the axial direction of the electric wireconductor 10, the applied forces may be changed during the pressingalong the axial direction.

The forces may be applied to the raw wire strand 10′, for example, bypassing the raw wire strand 10′ between the rollers disposed opposing toeach other. The raw wire strand 10′ is pressed with the rollers whileextruded along a rolling direction of the rollers, whereby it ispossible to sufficiently deform the outer shape of the entire raw wirestrand 10′ into a flat shape without applying a heavy load to the rawwire strand 10′, compared with drawing where a die is used to compressthe raw wire strand 10′ or pressing where a press machine is used tocompress the raw wire strand 10′. Further, it is easier to apply a loadevenly over the entire raw wire strand 10′ without concentrating a highload to a peripheral part of the raw wire strand 10′ in contact with therollers. As a result, by using the rollers for the pressing of the rawwire strand 10′, vacancies between the elemental wires 1 can besufficiently ensured in the flat cross section of the electric wireconductor 10 thus obtained, compared with a case where a die or apressing machine is used. Further, the deformation ratio of each of theelemental wires 1 including the elemental wire 1 located in theperipheral part of the electric wire conductor 10 can be kept low. Thevacancy ratio and the deformation ratio of each of the elemental wires 1may be adjusted by changing the magnitude of applying forces for thepressing (F1, F2, F3, F4, F1′, and F2′) and a shape of a part of theroller contacting the raw wire strand 10′.

By using the rollers, the raw wire strand 10′ as a whole can be formedinto a flat shape while the deformation ratios of the elemental wires 1are suppressed, whereby change in physical properties of the producedelectrical wire conductor 10 due to the deformation of the elementalwires 1 can be suppressed. Thus, in many cases, a process such as heattreatment for eliminating influence of processing distortion or workhardening is not particularly required for the electric wire conductor10 after the rolling.

In the electric wire conductor 10 formed by pressing of the raw wirestrand 10′, a compression ratio of the wire strand 10′ may be focused asan index for obtaining a desired vacancy ratio. The compression ratio isdefined by [1−(vacancy ratio of the obtained electric wireconductor)/(vacancy ratio of the wire strand)]×100%, and which may beregarded as a reduction rate of the conductor cross-sectional area. Asthe compression ratio is lowered, the electric wire conductor 10 obtainsa higher vacancy ratio. For example, if the compression ratio issuppressed to 70% or lower, and further to 65% or lower, a vacancy ratiosatisfying the above formula (1) may be obtained easily.

[Covered Electric Wire]

As described above, a covered electric wire 20 according to oneembodiment of the present invention contains the electric wire conductor10 according to the embodiment of the present invention as describedabove, and the insulator 21 which covers the outer periphery of theelectric wire conductor 10 (see FIGS. 5A and 5B, etc.).

An outer shape of the entire covered electric wire 20 including theinsulator 21 reflects the outer shape of the electric wire conductor 10.As the electric wire conductor 10 has a flat shape, the covered electricwire 20 also has a flat shape. Further, as the electric wire conductor10 has high flexibility in each direction, the covered electric wire 20also has high flexibility in each direction.

A material of the insulator 21 is not specifically limited, and avariety of polymer materials may be used to form the insulator 21.Further, the polymer material may contain fillers or additives asappropriate. However, it is preferable to select the material for theinsulator 21 and a thickness thereof such that the flexibility of theinsulator 21 is higher than the flexibility of the electric wireconductor 10, so as not to deteriorate the excellent flexibility of theelectric wire conductor 10. In addition, it is preferable to select thethickness of the insulator 21 such that the flat shape of the electricwire conductor 10 is sufficiently reflected to the shape of the entirecovered electric wire 20 so that the entire covered electric wire 20 hasa flat cross section.

The insulator 21 may cover a whole periphery of the electric wireconductor 10. In this case, the insulator 21 can be provided byextruding the polymer material for the insulator 21 on the wholeperiphery of the electric wire conductor 10. Alternatively, insulationfilms as the sheet-shaped insulators 21 may sandwich the electric wireconductor 10 from the top and the bottom in the height direction (±ydirection) of the electric wire conductor 10. In this case, two sheetsof insulation films made of polymer material are disposed at the top andbottom of the electric wire conductor 10 and may be adjoined each otherby fusing or adhesion, for example, as appropriate.

In the case where the electric wire conductor 10 is insulated using theinsulation films, laminating such as thermal lamination and drylamination may be utilized. For example, the insulation films made of apolyester resin are placed on both of the top and bottom sides of theconductor 10, and the spaces between the top and bottom insulation filmsand the spaces between the insulation films and the electric wireconductor 10 are joined with an adhesive.

Especially, where the insulator 21 is formed by extrusion, the electricwire conductor 10 having a flat cross section also promotes improvementof wear resistance of the insulator 21. Where an insulator is formed onthe outer periphery of an electric wire conductor having a substantiallycircular cross section, an irregular structure is likely to be formed onthe outer periphery of the electric wire conductor due to the shape ofelemental wires constituting the electric wire conductor, and thus theinsulator formed on each part of the outer periphery of the electricwire conductor is not likely to be uniform in thickness. Accordingly,even if the insulator has a portion at which the thickness is smallerthan other portions, a necessity arises to increase the thickness of theinsulator as a whole for obtaining a thickness satisfying predeterminedwear resistance. Meanwhile, on the outer surface of the electric wireconductor 10 having a flat shape, a flat surface is formed in the upperand lower direction (±y direction), and thus the insulator 21 coveringthe outer periphery of the electric wire conductor 10 can be effectivelyformed to have a uniform thickness at each portion. Accordingly, eventhough the thickness of the insulator 21 is made small as a whole, theinsulator 21 can easily keep the smallest thickness, required from theviewpoint of obtaining wear resistance, etc., at each portion of theouter periphery of the electric wire conductor 10. Thus, the coveredelectric wire 20 having the insulator 21 that is excellent in wearresistance is formed without increase of cost resulting from formationof a thick insulator 21 as a whole or increase of space to be requiredfor routing the covered electric wire 20.

Further, for a covered electric wire containing an electric wireconductor having a substantially circular cross section, the outersurface of an insulator contacts an external object with a small area,and a load tends to collectively applied to the small area. Meanwhile,for the covered electric wire 20 containing the electric wire conductor10 having a flat shape, the insulator 21 is formed along the flatsurface of the electric wire conductor 10, and thus exposure of theinsulator 21 tends to occur at its flat surface, and even where theinsulator 21 contacts an external object, the contact tends to occur inthe flat surface and in a large area. Consequently, the load applied dueto the contact may be dispersed into a large area, and thus although theinsulator 21 is formed to have a small thickness, it can effectivelyexhibit high wear resistance enough to resist wear due to application ofload.

Thus, by forming the covered electric wire 20 to contain the electricwire conductor 10 having a flat shape, even where the insulator 21 isformed to have a small thickness, the covered electric wire 20 can beformed to have the insulator 21 that is excellent in wear resistance dueto the effects of uniform thickness of the insulator 21 and the effectsof the insulator 21 capable of receiving contact with an external objectin a large area. The effects are further promoted by preventing burrsfrom formed on the outer periphery of the electric wire conductor 10.

The covered electric wire 20 may be used in a form of a single wire inwhich the outer periphery of one electric wire conductor 10 is coveredwith the insulator 21, or may be used in a form of a wiring harness inwhich a plurality of covered electric wires are assembled and integrallybundled with a covering material, for example, as necessary.Hereinafter, examples of the wiring harness containing the coveredelectric wires 20 will be described.

[Wiring Harness]

A wiring harness according to one embodiment of the present inventioncontains a plurality of covered electric wires being assembled, in whichat least a part of the plurality of covered electric wires are thecovered electric wires 20 according to the embodiment of the presentinvention containing the above-mentioned flat electric wire conductors10. The wiring harness may contain only the covered electric wires 20containing the above-mentioned flat electric wire conductors 10, or maycontain such covered electric wires 20 together with different kinds ofcovered electric wires such as a covered electric wire containing aconventional electric wire conductor having a substantially circularcross section. Further, in a case where the wiring harness contains aplurality of covered electric wires 20 containing the flat electric wireconductors 10, features such as a material, shape, and size of theelectric wire conductor 10 and the insulator 21 constituting theplurality of the covered electric wires 20 may be of the same or may bedifferent from each other. The plurality of covered electric wirecontained in the wiring harness may be integrally bundled with aninsulation material, for example, as necessary.

(1) Arrangement of the Covered Electric Wires in Wiring Harness

In the case of constructing a wiring harness with the plurality ofcovered electric wires 20 containing the flat electric wire conductors10, the plurality of covered electric wires 20 may be disposed in anypositional relationship. For example, the covered electric wires 20 maybe aligned side by side in the width direction x (the lateral direction)of the flat electric wire conductor 10 as shown in FIG. 5A, or may bestacked in the height direction y as shown in FIG. 5B, or may be in amatrix shape in which the plurality of covered electric wires 20disposed side by side in the width direction x are stacked in multiplelayers in the height direction y as shown in FIGS. 6A to 6C, and 8B.That is to say, the plurality of covered electric wires 20 may bealigned along at least either the width direction x or the heightdirection y. In this way, the neat arrangement of the plurality ofcovered electric wire 20 containing the flat electric wire conductors 10makes it possible to reduce spaces between the covered electric wires 20forming the wiring harness, thus providing the wiring harness with aremarkably excellent space-saving property.

In particular, in the case of disposing the plurality of coveredelectric wires 20 side by side in the width direction x of the flatelectric wire conductor 10, the space-saving property along the heightdirection y resulting from the flat shape of the electric wireconductors 10 may be effectively used in formation and routing of thewiring harness. The space-saving property can be effectively used, forexample, when the wiring harness is routed in a space of a limitedheight, or when other member is disposed above or below the wiringharness. Further, the heat dissipation performance of each of thecovered electric wires 20 can be effectively achieved.

In the case of disposing the plurality of covered electric wires 20 sideby side in the width direction, it is preferable that the heights H ofthe electric wire conductors 10 and the heights H′ of the coveredelectric wires 20 are respective uniform even where the plurality ofcovered electric wires 20 (20B) aligned along the width direction x ofthe wiring harness have different conductor cross-sectional areas. Withthe respective uniformity, the top and bottom surfaces of the wiringharness in the height direction are formed as flat surfaces. Here, theconcept that the heights H of the electric wire conductors 10 and theheights H′ of the covered electric wires are respective uniform means astate where height differences between the electric wire conductors 10are 10% or lower and height differences between the covered electricwires 20 are 10% or lower from the respective average heights.

Further, in the case of disposing the plurality of covered electricwires 20 side by side at least in the width direction to constitute thewiring harness, it is preferable that the insulator 21 covering theelectric wire conductors 10 aligned along the width direction is formedby the above described laminating using insulation films. In this case,the electric wire conductors 10 are aligned along the width direction xand laminating is performed with the electric wire conductors 10collectively sandwiched by two sheets of the insulation films from thetop and bottom directions, whereby the two sheets of the insulationfilms are adjoined each other by fusing or adhesion in the outerperipheral parts of the electric wire conductors 10 and positionsbetween the electric wire conductors 10. Thus, the electric wireconductors 10 aligned along the width direction x are insulated from theoutside using the insulation films, and a wiring harness that isinsulated by the insulation films and/or adhesion may be formed.

By performing laminating, the insulator covering is easily applied tothe electric wire conductors 10 aligned along the width direction x.Further, comparing with the case where the insulator covering isindividually applied to each electric wire conductor 10 by extrusion,the total thickness of the insulator 21 can be made small and aphenomenon of forming vacancy between an adjacent part and theindividual insulator 21 can be eliminated. Consequently, the wiringharness that is especially excellent in space-saving property may beformed.

As described above, in the wiring harness, the plurality of the coveredelectric wires 20 are aligned side by side in the width direction x andfurther stacked in multiple layers in the height direction y to have amatrix shape. In this case, the covered electric wires 20 disposed inthe width direction x may be treated as a unit and the same units areformed in multiple to be stacked in the height direction y, or thecovered electric wires 20 disposed in the width direction x may betreated as a unit and different types of units are formed in multiple tobe stacked in the height direction y. The specific examples of thelatter case are shown in FIGS. 6A to 6C.

In each of FIGS. 6A to 6C, a large cross-section covered electric wire20A having a large conductor cross-sectional area and the laterally-longelectric wire conductor 10 is disposed on a lower position in the heightdirection y, and a plurality of small cross-section covered electricwires 20B each having a smaller conductor cross-sectional area than thelarge cross-section covered electric wire 20 and the laterally-shortelectric wire conductor 10 are disposed on the upper position in theheight direction y. The plurality of small cross-section coveredelectric wires 20B are aligned side by side in the width direction xsuch that the lower surfaces of the aligned wires 20B are in contactwith the upper surface of the large cross-section covered electric wire20A. The large cross-section covered electric wire 20A and the smallcross-section covered electric wires 20B are stacked in multiple layersin the height direction to constitute the wiring harness, whereby thesmall cross-section covered electric wires 20 are disposed by utilizinga space over the large cross-section covered electric wire 20Beffectively, achieving an excellent space-saving property. Further, thesmall cross-section covered electric wires 20B are stably disposed dueto the large upper surface of the large cross-section covered electricwire 20B.

Herein, the plurality of small cross-section covered electric wires 20Bmay have the same conductor cross-sectional area as shown in FIGS. 6Aand 6C or have different conductor cross-sectional areas as shown inFIG. 6B. In either case, the space-saving property may be effectivelyimproved by uniformity of the height H of the electric wire conductors10 and the height H′ of the covered electric wires 20B in the smallcross-section covered electric wires 20B aligned along the widthdirection x. Further, it is preferable that the lateral width of thesmall cross-section covered electric wires 20B aligned along the widthdirection is the same as or smaller than the lateral width of the largecross-section covered electric wire 20A, and the small cross-sectioncovered electric wires 20B do not extend beyond the large cross-sectioncovered electric wire 20A in the width direction.

Further, the insulator covering may be applied individually to theelectric wire conductor 10 contained in each small cross-section coveredelectric wire 20B by such as extrusion, or it may be appliedcollectively to the plurality of the electric wire conductors 10 byperforming such as laminating. However, from the viewpoint of enhancingthe space saving of the wiring harness, and especially ensuring theflatness of the contact surface with the large cross-section coveredelectric wire 20A, it is preferable that the insulator covering iscollectively performed. In the configuration shown in FIG. 6C, theinsulator covering is collectively applied by laminating to the fourelectric wire conductors 10 disposed on the left side, and the threeelectric wire conductors 10 disposed on the right side for each group.

On the other hand, in the case where the plurality of covered electricwires 20 are arranged in the height direction y of the flat electricwire conductor 10, that is, stacked in multiple layers along the heightdirection y, the wiring harness can be constructed and routed whilekeeping a size in the width direction x of the entire wiring harnesssmall even when a size in the width direction x (the width W) of theelectric wire conductor 10 is large due to its flat shape. As a result,a space such as a long and thin space in the height direction can beutilized for routing.

In the wiring harness, disposing a heat dissipation sheet in contactwith each of the aligned covered electric wires 20 makes it possible toensure the heat dissipation performance of each of the covered electricwires 20, even when a great number of the covered electric wires 20 arealigned closely to one another by utilizing the flat shape. Here, theheat dissipation sheet is a sheet-shaped (including plate-shaped) memberconsisting of a heat dissipation material having a heat dissipationperformance higher than the covered electric wire 20. Examples of theheat dissipation sheet may include a sheet or a plate made of aluminumor an aluminum alloy. For example, the heat dissipation sheet may bedisposed between the plurality of covered electric wires 20 constitutingthe wiring harness, or disposed commonly contacting the plurality ofcovered electric wires 20.

As shown in FIG. 5A, in the case of aligning the plurality of coveredelectric wires 20 side by side in the width direction x, a heatdissipation sheet 31 is preferably disposed so as to commonly contactthe surfaces of the covered electric wires 20 along the width directionx (a flat surface). When the flat surface having a large area resultingfrom the flat shape of the electric wire conductor 10 is in contact witha surface on one side of the heat dissipation sheet, the heatdissipation performance of the covered electric wire 20 can beeffectively enhanced. Further, by commonly arranging the heatdissipation sheet 31 for the plurality of covered electric wires 20, theconfiguration of the wiring harness containing the heat dissipationsheet 31 can be simple. In the configuration illustrated in the figure,the covered electric wires 20 are not in contact with each other in thewidth direction x; however, when they contact with each other, it ispreferable that the heat dissipation sheets are also interposed betweenthe covered electric wires 20 adjacent to each other.

As shown in FIG. 5B, in the case of aligning the plurality of coveredelectric wires 20 in the height direction y, it is preferable to disposea heat dissipation sheet as an interposing sheet 32 to be disposedbetween each of the covered electric wires 20. The interposing sheets 32are in contact with flat surfaces of the respective covered electricwires 20 along the width direction x. The flat surface has a large areabecause of the flat shape of the electric wire conductor 10, and thus ittends to be difficult to outwardly dissipate heat generated byapplication of an electric current in the alignment where the pluralityof the covered electric wire 20 are disposed with the flat surfaces withlarge area close to or in contact with each other; however, theinterposing sheet 32 between the covered electric wires 20 promotes heatdissipation.

Further, the plurality of interposing sheets 32 disposed between therespective covered electric wires 20 are preferably connected with oneanother by a connection member 33 made of a heat dissipation material.The connection member 33 enhances the heat dissipation performance ofeach of the covered electric wires 20, compared with the case where onlythe interposing sheets 32 are disposed. The connection member 33 may bedisposed as a member specialized in heat dissipation of the coveredelectric wires 20 via the interposing sheets 32, or a member which isdisposed for another purpose. For example, a columnar memberconstituting an automobile body may be used as the connection member 33so that the member may serve as a structure material for the automobilebody, as the connection member 33 which helps the heat dissipation ofthe covered electric wires 20 via the interposing sheets 32, and furtheras a support member for supporting the wiring harness containing theplurality of covered electric wires 20.

As will be described in the Examples below, when the heat dissipationsheet 31 made of aluminum or an aluminum alloy is disposed in contactwith the flat surface of the covered electric wire 20 along the widthdirection x as shown in FIG. 5A, a cross-sectional area at a crosssection of the heat dissipation sheet 31 perpendicularly intersectingthe axial direction of the covered electric wire 20 is, for everycovered electric wire, preferably 1.5 times or larger, and morepreferably 4 times or larger of the cross-sectional area of the electricwire conductor 10 constituting the covered electric wire 20. Then, theheat dissipation performance of the covered electric wire 20 can beeffectively enhanced.

(2) Routing in an Automobile

As described above, when the wiring harness including the coveredelectric wires 20 having the flat electric wire conductor 10 is used,for example, as a wiring material for an automobile, it is possible toeffectively utilize the excellent space-saving property. Routing such awiring harness along a member such as floor and a frame of a vehiclemakes it possible to effectively utilize a limited space under the flooror around the frame for routing. Meanwhile, when the wiring harness isdisposed such that the width direction x of the electric wire conductor10 is approximately parallel to the surface of a floor or a framemember, more excellent space-saving property can be achieved.

A conventional wiring harness contains covered electric wires having asubstantially circular cross section bundled together, thus the entirewiring harness tends to be bulky. In order to produce a space forrouting in an automobile, a residential space (a space where a passengercan stay) is often reduced. However, as described above, when the wiringharness containing the covered electric wires 20 containing the flatelectric wire conductor 10 is used to keep the space necessary forrouting the wiring harness small, a large residential space can beprovided.

The wiring harness according to the present embodiment may be used in anautomobile as a wiring material for any purpose; and for example, it maybe used as a power-supply trunk line to be disposed under a floor. Aconventional power-supply trunk line for an automobile has been made ofa material which contains an insulation sheet and copper plates disposedside by side; however, continuously forming a large copper plate isdifficult and results in a low productivity. In addition, since thematerial contains a continuous metal body, fatigue fracture of thematerial possibly occurs due to influence of engine vibration of theautomobile, for example. In contrast, when the wiring harness accordingto the present embodiment constitutes a power-supply trunk wire, each ofthe process of forming the elemental wire 1 constituting the electricwire conductor 10, twisting the elemental wires 1, and forming the rawwire strand 10′ obtained through twisting of the elemental wires 1 intoa flat shape can be continuously performed for every portion of acontinuous material, thus achieving a high productivity. Further, as theelectric wire conductor 10 contains thin elemental wires 1, the entireelectric wire conductor 10 has a high durability against bending andvibration. Therefore, the fatigue fracture due to the engine vibration,for example, hardly occurs.

The wiring harness may not only be routed under the floor of theautomobile, but also form a floor or a ceiling itself with the wiringharness according to the present embodiment, for example. In anautomobile, the wiring harness needs to be routed so as not to interferewith components such as an engine; however, such a wiring route islimited. In particular, in an automobile requiring a large current suchas a hybrid vehicle and an electric vehicle, an electric wire with alarge conductor cross-sectional area is required to be routed, but awiring route capable of arranging the wiring harness including such anelectric wire with a large conductor cross-sectional area is limited.However, by constituting the floor or the ceiling with the wiringharness according to the present embodiment, the space can effectivelyprovide the wiring route, and also a large residential space can beensured, which leads to both the space-saving property and therequirement for application of a large electric current. Further, in acovered electric wire for a large electric current, an insulator easilydeteriorates due to a heat generated by an electric wire conductor;however, arranging the wiring harness as the floor and the ceiling caneffectively enhance heat dissipation performance. As a result, althoughan insulator 21 of low price with a comparatively low heat dissipationperformance is used to configure the covered electric wire 20,deterioration of the insulator 21 hardly occurs. Furthermore, as thecovered electric wire 20 containing the flat electric wire conductor 10has the flat surface, the covered electric wires 20 may be disposed invarious arrangements within a wiring harness, so that a combination ofthe flat surfaces enables the floor and the ceiling to have any surfaceshapes. When the wiring harness according to the present embodimentconstitutes the floor or the ceiling, a covering material may beappropriately arranged on the outer side of the wiring harness so as notto directly expose the wiring harness to a ceiling surface and a floorsurface.

Moreover, when the wiring harness according to the present embodiment isdisposed on the ceiling and the floor of the automobile, it ispreferable that the electric wire conductors 10 have a uniform height H,and the covered electric wires 20 have a uniform height H′, as shown inFIG. 7, even where the plurality of covered electric wires 20 formingthe wiring harness have different conductor cross-sectional areas.Accordingly, upper and lower surfaces in the height direction of thewiring harness may be configured flat, whereby a high space-savingproperty is achieved in the height direction when the wiring harness isrouted along the ceiling surface and the floor surface. Also, anirregular structure in the height direction of the wiring harness hardlyaffects interior design of the automobile or functions of adjacentmembers.

As shown in FIG. 7, it is preferable that the wiring harness in whichthe height H of the electric wire conductors and the height H′ of thecovered electric wires 20 are respective uniform as described above isdisposed, for example, between an interior member 51 forming the flooror the ceiling of the automobile and a sound absorbing member 52disposed adjacent to an outer side of the interior member 51 (on anopposite side of the residential space) such that the flat surfaces ofthe wiring harness along the width direction x are disposed alongsurfaces of the interior member 51 and the sound absorbing member 52.Then, a small space between the interior member 51 and the soundabsorbing member 52 can be effectively utilized for routing the wiringharness. As the height H′ of the covered electric wires 20 is uniform,the wiring harness can be arranged without unnecessarily increasing adistance between the interior member 51 and the sound absorbing member52. Further, a possible problem may be prevented where an irregularstructure in the height direction of the wiring harness appears as anirregular structure on the surface of the interior member 51 todeteriorate a surface design of the interior member 51. Furthermore,another possible problem may be prevented where the covered electricwires 20 with a large and non-uniform height H′ press the surface of thesound absorbing member 52 to affect a performance of the sound absorbingmember 52, including nonuniformity in a sound absorbing property. Here,examples of a combination of the interior member 51 and the soundabsorbing member 52 may include a combination of a floor carpet and asilencer.

Moreover, the wiring harness according to the present embodiment may berouted in the automobile while using a variety of members constitutingthe automobile body as a supporting member. For example, as shown inFIG. 8A, the wiring harness may be disposed along an outer periphery ofa columnar member constituting the automobile body. The wiring harnessmay be disposed so that a surface along the width direction x of each ofthe covered electric wires 20 forming the wiring harness is arrangedalong an outer peripheral surface of the columnar member 41.Alternatively, as shown in FIG. 8B, the wiring harness may be disposedin a continuous member having a cross section intersecting thelongitudinal direction in a substantially U-shape or a channel shape, inother words, the wiring harness may be disposed in a hollow part 42 b ofa hollow tubular member 42 having an opening 42 a along the longitudinaldirection. The wiring harness may be configured in which the pluralityof covered electric wires 20 are aligned in the width x direction and/orthe height y direction in accordance with shapes of the opening 42 a andthe hollow part 42 b. As described above, the heat dissipation sheetsmay be disposed as appropriate between the aligned covered electricwires 20. Examples of the columnar member 41 and the tubular member 42include a member used as a reinforcement which is disposed in a frontside of an instrument panel of automobiles.

(3) Combination with Other Electric Wires

As described above, the wiring harness according to an embodiment of thepresent invention may contain the covered electric wires 20 containingthe flat electric wire conductor 10 according to an embodiment of thepresent invention in combination with other kinds of covered electricwires. The covered electric wires 20 according to an embodiment of thepresent invention and other kinds of covered electric wires may havecombination of specific features such as constituent material, shape,and size. Among them, examples may include a configuration using thecovered electric wire conductor 20 according to an embodiment of thepresent invention (i.e., a first covered electric wire) containing theflat electric wire conductor 10 made of aluminum or an aluminum alloy(i.e., aluminum material), and other kinds of covered electric wire(i.e., a second covered electric wire) containing an electric wireconductor made of copper or a copper alloy (i.e., copper material)having a substantially circular cross section, for example, with theflatness lower than the electric wire conductor 10 of the first coveredelectric wire 20. In this case, it is preferable that a conductorcross-sectional area of the second covered electric wire is smaller thana conductor cross-sectional area of the first covered electric wire 20.

The aluminum material has come to be used as an electric wire conductivematerial for automobiles instead of the copper material for the purposeof reducing automobile weight; however, as described above, in the casewhere the aluminum material is used, the conductor cross-sectional areaof the electric wire conductor tends to be larger than in the case wherethe copper material is used, because the aluminum material has a lowerelectrical conductivity as a material. Thus, if the electric wireconductor made of an aluminum material is used as a conventionalconductor having a circular cross section and contained in the wiringharness, a diameter of the electric wire conductor becomes large, whichrequires a large space for routing the wiring harness; however, the flatelectric wire conductor 10 can reduce the space required for routingwhile ensuring the large conductor cross-sectional area. On the otherhand, even the electric wire conductor made of the copper material isused, it does not significantly interfere the weight reduction ofautomobiles as long as it is a small diameter wire with a smallconductor cross-sectional area. Also, it hardly enlarges space requiredfor routing the wiring harness. Accordingly, using the first coveredelectric wire 20 including the flat electric wire conductor 10 made ofthe aluminum material in combination with the second covered electricwire including the electric wire conductor having a substantiallycircular cross section made of the copper material with a smallerconductor cross-sectional area, excellent properties of the coppermaterial such as a high electrical conductivity may be utilized as aproperty of a part of the wiring harness while ensuring the space-savingproperty. Suitable examples of the electric wire conductor constitutingthe second covered electric wire may include a copper alloy thin wirewith a conductor cross-sectional area of 0.13 mm² or smaller. Such acopper alloy thin wire may be suitably used as a signal wire. Formingthe second covered electric wire into thin as described above makes itpossible to effectively utilize the space-saving property brought aboutby the flat electric wire conductor 10 contained in the first coveredelectric wire 20. The relative arrangements of the first coveredelectric wire and the second covered electric wire are not particularlylimited. However, similarly with the arrangement shown in FIGS. 6A to6C, examples of the relative arrangements include a state in which theplurality of the second covered electric wires having a lower flatnessand a smaller conductor cross-sectional area are aligned on the firstcovered electric wire 20 having a higher flatness and a larger conductorcross-sectional area.

EXAMPLE

Hereinafter, examples according to an embodiment of the presentinvention are explained. It should be noted that the present inventionis not limited by these examples.

[State of Vacancies in Cross section of Electric Wire Conductor]

For a cross section of an electric wire conductor formed into flat,state of vacancies was investigated.

(Test Method)

A raw wire strand was prepared by twisting aluminum alloy wires havingan outer diameter of 0.32 mm to form a conductor cross-sectional area inthe range of 2 to 60 mm² and a substantially circular cross-sectionalshape.

The raw wire strand was subjected to pressing with rollers to prepare anelectric wire conductor having a substantially rectangular crosssection. The pressing with the roller was carried out, as shown in FIG.3, by firstly applying forces F1 and F2 from upper and lower directions,then applying forces F1′ and F2′ again from the same directions, andsimultaneously applying forces F3 and F4 from both sides of a widthdirection. In this process, the applying forces were varied to prepareelectric wire conductors having different compression ratios (reductionrate of a cross-sectional area) Then, an outer periphery of eachelectric wire conductor was covered with an insulator containingpolyvinyl chloride (PVC) to form a sample of a covered electric wire.The thickness of the insulator was in the range of 0.2 to 2.0 mmdepending on the conductor cross sectional area. For example, thethickness of the insulator was 1.5 mm where the conductorcross-sectional area was 60 mm².

Each of the covered electric wires was embedded in an epoxy-based resin,and a cross section intersecting an axial direction was polished toprepare a cross-sectional sample. Then, the obtained cross-sectionalsamples were photographed.

Photographic images of the cross sections were subjected to imageanalysis to evaluate vacancy ratios. In the analysis, a cross-sectionalarea of the entire electric wire conductor (A0) was estimated from anarea of a region inside an outline connecting outlines of elementalwires located at an outermost periphery of the electric wire conductor,and within the above-described region, an area of vacancies (A1) wasestimated from an area of a region that was not occupied by theelemental wires. A vacancy ratio (A1/A0×100%) was calculated.

(Test Results)

FIGS. 9A to 9F show photographic images of the cross sections ofrepresentative samples of the covered electric wires, and values ofvacancy ratios. FIGS. 9A to 9C show samples each having the conductorcross-sectional area of 60 mm², while FIGS. 9D to 9F show samples eachhaving the conductor cross-sectional area of 15 mm². The compressionratios were the following order from the lowest in FIGS. 9A to 9C: FIGS.9A, 9B, and 9C. The compression ratios were the following order from thelowest in FIGS. 9D to 9F: FIGS. 9D, 9E, and 9F.

Comparing the cross-sectional images in FIGS. 9A to 9C, comparativelylarge vacancies were formed between the elemental wires in FIGS. 9A and9B, while the elemental wires were densely filled in FIG. 9C. Thesefeatures were more apparent through the obtained values of vacancyratios. The vacancy ratio was 20% or higher in FIGS. 9A and 9B, whilethe vacancy ratio was 20% or lower in FIG. 9C. Comparing FIG. 9A and 9B,the vacancy ratio was lower in FIG. 9B in which compression wasperformed at a higher rate.

In addition, in FIG. 9A, as can be seen from the portion pointed by anarrow, many continuous vacancies capable of accommodating two or more ofelemental wires were present. In FIG. 9B, continuous vacancies capableof accommodating at least one or more elemental wires were present. Incontrast, such large continuous vacancies were hardly found in FIG. 9C.

Further, in FIGS. 9A and 9B, the peripheral parts of the electric wireconductors were formed smoothly, while in FIG. 9C, a sharp burr wasproduced at end parts in the width direction as indicated by a circle.Thus, it is apparent that an electric wire conductor having a highvacancy ratio allows the conductor to be favorably formed to have asmooth outer surface without burrs.

Also in the samples shown in FIGS. 9D to 9F each having a lowerconductor cross-sectional area, the same features as in FIGS. 9A to 9Cwere observed. That is, as in FIGS. 9D and 9E, where the electric wireconductor has a higher vacancy ratio, the conductor may be favorablyformed to have a smooth outer surface without burrs. However, as in FIG.9F, where the electric wire conductor has a lower vacancy ratio, sharpburrs as indicated by circles were formed at the outer peripheral part.

Also for electric wire conductors having different conductorcross-sectional areas, a vacancy ratio of the conductor was similarlyevaluated in cross section after compression. The results weresummarized in FIG. 10. In FIG. 10, the horizontal axis represents aconductor cross-sectional area and the vertical axis represents avacancy ratio. A sample in which no burrs were formed on the outerperiphery of the electrical wire conductor as shown in FIGS. 9A, 9B, 9Dand 9E was evaluated as “passed” and indicated with a circle. Among thesamples evaluated as “passed”, a sample having the lowest vacancy ratioin samples of the same conductor cross-sectional area was indicated by ablack circle mark. A sample in which burrs were formed on the outerperiphery of the electrical wire conductor as shown in FIGS. 9C and 9Fwas evaluated as “failed” and indicated by a square mark.

FIG. 10 appears that larger the conductor cross-sectional area (s) ofthe electric wire conductor is, higher the vacancy ratio (v) requiredfor the covered electric wire to be evaluated as passed becomes. In FIG.10, linear lines represented by v=0.29 s+A are illustrated. As indicatedon the right side of the Figure, intercept A was changed into one ofthree numbers: A=2.0 (solid line); A=2.5 (dotted line) and A=3.5 (brokenline). Failure points (square marks) locate below the linear linewherein A=2.0. Pass points (black circle marks or white circle marks)locate above the linear line wherein A=2.5, and especially the pointsindicating the lowest vacancy ratio among the respective conductorcross-sectional areas (indicated by black circle marks) are close to thelinear line wherein A=3.5

(Distribution of Deformation Ratio of Elemental Wires)

Next, distribution of the deformation ratio of elemental wires wasobserved for the cross section of the electric wire conductor formed tohave a flat cross-sectional shape.

(Test Method)

An electric wire conductor having a flat cross section and consisting ofan aluminum alloy was prepared in the same manner as in the test “Stateof Vacancies in Cross section of Electric Wire Conductor” describedabove. Further, insulator coverings were provided to prepare a coveredelectric wire in the same manner as described above. Then, a sample forcross section observation was prepared and cross section of the samplewas photographed.

(Test Results)

As for the cross-sectional images obtained through the test forinvestigating vacancies as described above and shown in FIGS. 9A to 9F,the shapes of the elemental wires located on the peripheral parts andthe center part in cross section were compared through visualobservation. In FIGS. 9A, 9B, and 9D, the deformation of the elementalwires was apparently smaller at the peripheral parts, especially in aregion located at end parts in the width direction than at the centerpart. Further, when focusing on a region located at end parts of theperipheral part in FIG. 9E, the deformation of the elemental wires wassmaller in the region than at the center part. In contrast, in FIGS. 9Cand 9F, it was visually confirmed that the deformation of the elementalwires was larger at the peripheral parts than at the center part. Thus,it was confirmed that in the electric wire conductor having a highvacancy ratio and having no burrs at its outer peripheral surface,deformation of the elemental wires was smaller at the peripheral partsthan at the inner parts also in portions other than portion where burrswere likely to be formed.

To confirm the tendency, a deformation ratio of the elemental wires ofthe electric wire conductor was evaluated quantitatively at theperipheral part and the center part and compared. The photographicimages shown in FIG. 11A to 11E were used for the evaluation. FIG. 11Ashows the cross section of a raw wire strand before compression. FIGS.11B and 11C show electric wire conductors each having a conductorcross-sectional area of 60 mm² after compression, and show the samesamples in FIGS. 9A and 9C, respectively. FIG. 11D shows an electricwire conductor having a conductor cross-sectional area of 30 mm² aftercompression. FIG. 11E shows an electric wire conductor having aconductor cross-sectional area of 15 mm² after compression. The electricwire conductors in FIGS. 11D and 11E are different samples from thesamples shown in FIGS. 9A to 9F, and FIG. 10. In the samples shown inFIGS. 11B, 11D, and 11E, no burrs were formed on the respective outersurfaces, while in the sample shown in FIG. 11C, burrs were formed onthe outer surface as indicated by a circle.

Image analysis was performed for each cross-sectional image shown inFIGS. 11B to 11E to obtain a deformation ratio of the elemental wires.In this case, the deformation ratio of the elemental wires wascalculated according to the above formula (4). As a diameter R definedas a diameter of a circle, 0.32 mm, the outer diameter of a raw wirestrand before compression, was adopted. The deformation ratio of theelemental wires was obtained for the wires located at the peripheralpart (end portions) and indicated as a rectangular region R1 in eachcross-sectional image, and for the wires located at the center part andindicated as a rectangular region R2 in each cross-sectional image. Thenan average deformation ratio was obtained for each region. Further, aperipheral deformation ratio was obtained which is a ratio of thedeformation ratio at the peripheral parts to the deformation ratio atthe center part (deformation ratio at the peripheral part/deformationratio at the center part×100%). Table 1 shows thus obtained evaluationresults.

TABLE 1 Conductor Deformation ratio of elemental wires cross-sectionalPeripheral area deformation Figures [mm²] Peripheral part Center partratio 11B 60 3.8% 21%  18% 11C  21% 21% 100% 11D 30  19% 30%  63% 11E 15 17% 26%  65%

Comparing the evaluation results of FIGS. 11B and 11C having the sameconductor cross-sectional area, in photographic images, the crosssection of each elemental wire was not significantly deformed from asubstantially circular shape before pressed in FIG. 11B, while manyelemental wires were significantly deformed from a circular shape inFIG. 11C. According to the results of the image analysis in Table 1, inFIGS. 11B and 11C, the deformation ratios of the electric wireconductors were equal at the center part while they were significantlydifferent at the peripheral part. In FIG. 11B, the deformation ratio waslower at the peripheral part than at the center part, and thedeformation ratio at the peripheral part was compressed to 18% withrespect to the value at the center part. In contrast, in FIG. 11C, thedeformation ratio is the same between the peripheral part and the centerpart.

Thus, it was confirmed that where a compression ratio was low and noburrs were formed on the electric wire conductor, large vacancies wereobtained in cross section and the deformation ratio of the elementalwires was lower at the peripheral part than at the center part. Further,in the electric wire conductors having a small conductor cross-sectionalarea as shown in FIGS. 11D and 11E, a deformation ratio of the elementalwires was also lower at the peripheral part than at the center part ifno burrs were formed on the electric wire conductor.

[Flexibility of Covered Electric Wire]

Influence of a cross-sectional shape of the electric wire conductor toflexibility of the covered electric wire was examined.

(Test Method)

An electric wire conductor having a substantially circular cross sectionand an electric wire conductor having a flat cross section bothconsisting of an aluminum alloy were prepared in the same manner as inthe test “State of Vacancies in Cross section of Electric WireConductor” described above. Further, insulator covering were provided toprepare covered electric wires in the same manner as above. Conductorcross-sectional areas of the electric wire conductors were 35 mm² or 130mm², respectively. An aspect ratio of the flat cross section was 1:3 forthe conductor cross-sectional area of 35 mm², and 1:4 for the conductorcross-sectional area of 130 mm².

For each of the covered electric wires thus prepared, flexibility wasevaluated by measuring an opposing force. Three-point bending wascarried out for measuring the opposing force. That is, both ends of acovered electric wire having a length of 100 mm were held firmly, and anopposing force incurred by bending a center part was measured with aload cell.

(Test Results)

Table 2 below shows measurement results of the opposing force obtainedfor each of the covered electric wires.

TABLE 2 Conductor cross-sectional Cross-sectional area shape Opposingforce (N)  35 mm² Circular  32 Flat (1:3)  25 130 mm² Circular 102 Flat(1:4)  88

According to Table 2, for each conductor cross-sectional areas, theopposing force was reduced when the sectional shape was changed fromcircular to flat. In other words, flexibility was enhanced. Even in thecase where the conductor cross-sectional area was as large as 130 mm²,flexibility was enhanced by flattening. In each of the conductorcross-sectional areas, the opposing force was reduced to 90% or lower byflattening; however, in the case of the large conductor cross-sectionalarea, the aspect ratio of the flat shape needs to be higher (width needsto be wider) to improve flexibility to the same degree.

[Heat Dissipation Performance of Covered Electric Wire]

A relationship between a heat dissipation performance of the coveredelectric wire and the shape of the electric wire conductor as well aspresence or absence of a heat dissipation sheet was examined by computersimulations.

(Test Method)

A computer simulation employing a thermal conductivity analysisaccording to a finite element method was used to estimate a degree oftemperature rise upon application of an electric current to a coveredelectric wire. Specifically, the covered electric wire was assumed as asample, in which an insulation cover made of PVC having a thickness of1.6 mm was formed on an outer periphery of three types of the electricwire conductors made of a copper alloy; one had a circular crosssection, one had a flat cross section with an aspect ratio of 1:3, andone had a flat cross section with an aspect ratio of 1:5. For theconductor having the circular cross section, a conductor cross-sectionalarea was set to 134.5 mm², and for the conductor having the flat crosssections, conductor cross-sectional areas were set to have threedifferent values based on 134.5 mm². Then, a current of 400 A wasapplied to each of the samples and a temperature rise for achieving asteady state was estimated by the simulation. A temperature of thesurrounding environment was set at 40 degrees C.

In addition, for the covered electric wire having a flat electric wireconductor with an aspect ratio of 1:5, a temperature rise was similarlyestimated also for a case where a heat dissipation sheet was disposed.As the heat dissipation sheet, two types of aluminum plates with athickness of 5 mm, having a width of 30 mm and 60 mm were employed. Aflat surface of the covered electric wire along the width direction xwas brought into close contact with a surface of one side of the heatdissipation sheet while aligning the center of the covered electric wirein the width direction x with the center of the heat dissipation sheetin the width direction.

(Test Results)

Values of temperature rise obtained by the simulation for each of thesamples are expressed in FIG. 12 as a function of a conductorcross-sectional area. FIG. 12 also shows approximate curves for thevalues.

According to FIG. 12, the temperature rise of the electric wireconductor having a flat cross section was kept lower than that of theelectric wire conductor having a substantially circular cross section,that is, the heat dissipation performance was enhanced. In particular,as the aspect ratio of the flat shape was increased (the width wasincreased), the heat dissipation performance was enhanced. As a result,when an upper limit of the temperature rise was set at a predeterminedtemperature, the temperature rise may be suppressed below the upperlimit by forming the cross section of the electric wire conductor intoflat and further by making the aspect ratio high, even if the conductorcross-sectional area of the electric wire conductor was made small. Forexample, when the upper limit of the temperature rise was set at 40degrees C., a lower limit of the conductor cross-sectional area was,approximately 135 mm² for the circular cross section, approximately 125mm² for the flat cross section with the aspect ratio of 1:3, andapproximately 120 mm² for the flat cross section with the aspect ratioof 1:5.

Further, when the heat dissipation sheet was disposed on the coveredelectric wire having a flat cross section, the heat dissipationperformance was further enhanced. In particular, the larger thecross-sectional area of the heat dissipation sheet was, the higher theheat dissipation performance improved. That is to say, when the upperlimit of the temperature rise was set at a predetermined temperature, aheat dissipation sheet having a large cross-sectional area couldsuppress the temperature rise below the upper limit, even if theconductor cross-sectional area of the electric wire conductor was madesmall. For example, when the upper limit of the temperature rise was setat 40 degrees C. and a width of the heat dissipation sheet was 30 mm, alower limit of the conductor cross-sectional area was approximately 95mm². In this case, the cross-sectional area of the heat dissipationsheet was approximately 1.6 times larger than the conductorcross-sectional area. On the other hand, when the width of the heatdissipation sheet was 60 mm, the lower limit of the conductorcross-sectional area was 67 mm². In this case, the cross-sectional areaof the heat dissipation sheet was approximately 4.5 times larger thanthe conductor cross-sectional area.

[Wear Resistance of Insulator]

Finally, the effects of cross-sectional shape of the electric wireconductor on wear resistance of the insulator were examined for thecovered electric wire.

[Test Method]

An electric wire conductor having a circular cross section consisting ofan aluminum alloy was prepared in the same manner as in the test of“State of Vacancies in Cross section of Electric Wire Conductor”described above. Cross-sectional area of the electric wire conductor was15 mm². The electric wire conductor having a circular cross section wascompressed to have a flat cross section with an aspect ratio of 1:4.

The outer periphery of the electric wire conductor having a circularcross section and the outer periphery of the electric wire conductorhaving a flat cross section are both covered with an insulator to formthe following three types of samples. In each sample, the covering ofthe outer periphery of the electric wire conductor with an insulator wasperformed by extruding polyvinyl chloride.

Sample 1: An insulator was provided on the outer periphery of theelectric wire conductor having a flat cross section. The smallest valueof the thickness of the insulator covering (the smallest thickness ofthe insulator) was 0.6 mm.

Sample 2: An insulator was provided on the outer periphery of theelectric wire conductor having a circular cross section. The smallestthickness of the insulator was 1.0 mm.

Sample 3: An insulator was provided on the outer periphery of theelectric wire conductor having a circular cross section. The smallestthickness of the insulator was 0.6 mm.

For each of samples 1 to 3, the height of the wire was measured (lengthin the upper and lower direction of the covered electric wire). Further,wear resistance was evaluated by tape test according to JASO D 618. Forthe evaluation, apart of each sample of the covered electric wire wascut out to have a length of 1000 mm, and a wear tape #150G was pressedonto the cut-out wire with a pressing load of 1.9 kg. Then, the tape wasdelivered at the moving speed of 1500 mm/min, and the length of the tapedelivered till the electric wire conductor was exposed was measured. Thewear resistance was evaluated as excellent “A” where the length of thedelivered tape was 635 mm or longer, and the wear resistance wasevaluated as fallen “B” where the length of the delivered tape wasshorter than 635 mm.

(Test Results)

Cross-sectional images of samples 1 to 3 were shown in FIGS. 13A to 13C.The configuration of each sample and the test results are summarized inthe below Table 3.

TABLE 3 Sample 1 Sample 2 Sample 3 Cross-sectional Flat CircularCircular shape of conductor Conductor 15 mm² cross-sectional areaSmallest thickness 0.6 mm 1.0 mm 0.6 mm of insulator Height of wire 3.2mm 7.5 mm 6.7 mm Tape wear test A A B

When viewing the cross-sectional images in FIGS. 13A to 13C, in Samples2 and 3 of electric wire conductors each having a circular crosssection, the peripheral parts of the conductors were irregular with adegree to accommodate two elemental wires in outer diameter at most dueto the shape of the elemental wires. Accordingly, thickness distributionof the insulator provided on the outer periphery of the electric wireconductor was formed for each portion. In contrast, in Sample 1 of anelectric wire conductor having a flat cross section, the peripheralpart, especially the upper and lower edges, was flat. Accordingly, theinsulator covering the outer periphery of the electric wire conductorwas formed to have a flat shape, and thickness distribution for eachportion of the insulator was small. Through the comparison of samples 1to 3, it was confirmed that by forming the electric wire conductor tohave a flat cross section, the insulator covering is formed to be flatand have high uniformity in thickness with maintaining a predeterminedsmallest thickness, compared with the circular cross section

Further, comparing the results of the tape-wear test in Table 3, eventhough Samples 1 and 3 maintained the same smallest thickness of theconductor, Sample 1 of the electric wire conductor having a flat crosssection obtained excellent wear resistance while Sample 3 of theelectric wire conductor having a circular cross section could not obtainsufficient wear resistance. It can be construed that where the electricwire conductor had a flat cross section, the insulator provided on theouter periphery of the conductor had a flat surface, had a planercontact with a tape, and a load applied to the insulator could bedispersed, and where the electric wire conductor had a circular crosssection, the insulator had a contact with a tape in a small area, and aload applied to the insulator was concentrated on a small area. Sample 2showed excellent wear resistance even though it had a circular crosssection of conductor. However, comparing with Sample 1, the smallestthickness of conductor was larger in Sample 2, and thus the height ofthe wire was large.

As described above, it was confirmed that by utilizing an electric wireconductor having a flat cross section, a covered electric wire is formedto be flat and have a uniform thickness easily. Consequently, sufficientwear resistance can be effectively obtained with a smallest thickness ofan insulator or the thickness of the entire insulator made small,achieving both the space-saving and wear-resistance properties.

Although embodiments of the present invention have been described abovein detail, the present invention is not limited to the particularembodiment(s) disclosed herein, and various changes and modificationsmay be made without deviating from the scope of the present invention.

In addition, an embodiment has been described where the electric wireconductor has the vacancy ratio of equal to or more than a predeterminedvalue; however, an embodiment of the electric wire conductor does nothave the vacancy ratio described above may be presented, that is, anelectric wire conductor which contains a wire strand having a pluralityof elemental wires twisted together, and has a flat portion where across section intersecting an axial direction of the wire strand isflat. Also in such an embodiment, forming the cross-sectional shape intoflat makes it possible to achieve both the improved flexibility and thespace-saving property compared with a case of the substantially circularcross section. Further, also in such an embodiment, the above-mentionedfeatures relating to the electric wire conductor other than the vacancyratio can be suitably applied, for example, the cross-sectional shape ofeach elemental wire such as the deformation ratio, the material and theconductor cross-sectional area of the electric wire conductor, theaspect ratio of the electric wire conductor, and arrangement of both theflat portion and the low-flatness portion. Furthermore, also thefeatures relating to the covered electric wire and the wiring harness asdescribed above can be suitably applied.

Especially, even where the flat portion of the electric wire conductordoes not have the vacancy ratio as described above, by making thedeformation ratio of the elemental wires lower at the peripheral partthan at the center part, the flexibility of the conductor may beimproved comparing with the case where the deformation ratio of theelemental wires at the peripheral part is equal to or higher than theone at the center part. In such case, favorable values of the parametersrelated with the deformation ratios of the elemental wires, such as theperipheral part deformation ratio of the elemental wires, and thedeformation ratios of the elemental wires at the peripheral part and thecenter part, are the same as described above.

Even where the vacancy ratio in the entire cross section of the electricwire conductor does not satisfy the relation according to the aboveformula (1), when the cross section of the conductor contains continuousvacancies capable of accommodating one or more of the elemental wire 1or continuous vacancies having an area equal to the area of one or moreof the elemental wire 1 in cross section, the flexibility of theelectric wire conductor can be improved compared with the case wheresuch continuous vacancies are not contained. In such case, favorablevalues of the parameters related with the shape and the area of thecontinuous vacancies are the same as described above.

LIST OF REFERENCE NUMERALS

-   1 Elemental wire-   10 Electric wire conductor-   10′ Raw wire strand-   20 Covered electric wire-   20A Large cross-section covered electric wire-   20B Small cross-section covered electric wire-   21 Insulator-   H Height of electric wire conductor-   H′ Height of covered electric wire-   W Width of electric wire conductor-   x Width direction-   y Height direction-   31 Heat Dissipation sheet-   32 Interposing sheet (Heat Dissipation sheet)-   33 Connection member-   41 Columnar member-   42 Tubular member-   51 Interior member-   52 Sound absorbing member

1. An electric wire conductor comprising a wire strand comprising aplurality of elemental wires twisted together, the conductor having aflat portion where a cross section of the wire strand intersecting anaxial direction of the wire strand has a flat shape, wherein assuming aconductor cross-sectional area of the flat portion as s mm² and avacancy ratio defined as a ratio of vacancies not occupied by theelemental wires in a cross section of the flat portion as v %, theconductor cross-sectional area and the vacancy ratio satisfies v>0.29s+2.0.
 2. The electric wire conductor according to claim 1, wherein theconductor cross-sectional area and the vacancy ratio satisfies v≥0.29s+2.5.
 3. The electric wire conductor according to claim 1, whereindeformation ratios of the elemental wires from a circle in the crosssection of the flat portion are lower at a part facing an outerperiphery of the flat portion than at a center part of the flat portion.4. The electric wire conductor according to claim 1, wherein deformationratios of the elemental wires from a circle in the cross section of theflat portion at a part facing an outer periphery of the flat portion are65% or lower of the deformation ratios of the elemental wires at acenter part of the flat portion.
 5. The electric wire conductoraccording to claim 1, wherein deformation ratios of the elemental wiresfrom a circle in the cross section of the flat portion at a part facingan outer periphery of the flat portion are 20% or lower.
 6. The electricwire conductor according to claim 1, wherein the cross section of theflat portion comprises a continuous vacancy capable of accommodating oneor more of the elemental wires.
 7. The electric wire conductor accordingto claim 1, wherein the cross section of the flat portion includesopposing edges along a width direction of the flat shape being parallelto each other; and deformation ratios of the elemental wires from acircle in the cross section of the flat portion are lower at end partsof the opposing edges of the flat portion than at a center part of theflat portion.
 8. The electric wire conductor according to claim 1,further comprising a low-flatness portion having a flatness lower thanthe flat portion, the flat portion and the low-flatness portioncontinuously disposed in the axial direction.
 9. The electric wireconductor according to claim 1, wherein the number of the elementalwires contained in the wire strand is 50 or more.
 10. A covered electricwire comprising: the electric wire conductor according to claim 1; andan insulator covering the electric wire conductor.
 11. A wiring harnesscomprising the covered electric wire according to claim
 10. 12. A wiringharness comprising a plurality of the covered electric wires accordingto claim 10, wherein the plurality of the covered electric wire arealigned along at least one of a width direction of the electric wireconductor and a height direction intersecting the width direction. 13.The wiring harness according to claim 12, further comprising at leastone of a heat dissipation sheet disposed between the plurality of thecovered electric wire and a heat dissipation sheet commonly contactingthe plurality of the covered electric wire.
 14. The wiring harnessaccording to claim 12, wherein the plurality of the covered electricwire are aligned at least along the height direction.
 15. The wiringharness according to claim 14, further comprising interposing sheetsmade of a heat dissipation material disposed between the plurality ofthe covered electric wire aligned along the height direction; and aconnection member made of a heat dissipation material connecting theinterposing sheets mutually.
 16. The wiring harness according to claim12, wherein the plurality of the covered electric wire are aligned atleast along the width direction, the insulator is made of insulationfilms bonded to each other by fusion or by adhesive while sandwichingthe electric wire conductors aligned along the width direction alltogether in between the height direction, and the electric wireconductors are insulated mutually by the insulation film or theadhesive.
 17. The wiring harness according to claim 12, wherein theplurality of covered electric wire includes a large cross-sectioncovered electric wire and a plurality of small cross-section coveredelectric wires each having a conductor cross-sectional area smaller thanthe large cross-section covered electric wire, the small cross-sectioncovered electric wires have a uniform height, and the largecross-section covered electric wire and the small cross-section coveredelectric wires are stacked in the height direction with the smallcross-section covered electric wires are aligned along the widthdirection.
 18. The wiring harness according to claim 11, wherein thecovered electric wire includes a first covered electric wire and asecond covered electric wire, the electric wire conductor of the firstcovered electric wire is made of aluminum or an aluminum alloy, and theelectric wire conductor of the second covered electric wire is made ofcopper or a copper alloy having a lower flatness and a smallercross-sectional area than the electric wire conductor of the firstcovered electric wire.
 19. The wiring harness according to claim 18,wherein the conductor cross-sectional area of the second coveredelectric wire is 0.13 mm² or smaller.